Reproduced here; the steps are:
  1) Open gamix
  2) Click on the 'prog' menu
  3) Click on the 'config' option in that menu
  4) It crashes.

bt full:

(gdb) bt full
#0  0x00007ffff64f2d05 in raise (sig=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:64                                                        
        resultvar = 0                                                                                                                        
        pid = <value optimised out>
        selftid = 14765
#1  0x00007ffff64f6ab6 in abort () at abort.c:92
        save_stage = 2
        act = {__sigaction_handler = {sa_handler = 0x1300000022, sa_sigaction = 0x1300000022}, sa_mask = {__val = {140737488340496, 
              140737488348155, 14, 140737326951300, 3, 140737488340490, 6, 140737326951304, 2, 140737488340478, 2, 140737326942293, 1, 
              140737326951300, 3, 140737488340484}}, sa_flags = 12, sa_restorer = 0x7ffff6612b88}
        sigs = {__val = {32, 0 <repeats 15 times>}}
#2  0x00007ffff652bd7b in __libc_message (do_abort=2, fmt=0x7ffff6614400 "*** glibc detected *** %s: %s: 0x%s ***\n")
    at ../sysdeps/unix/sysv/linux/libc_fatal.c:189
        ap = {{gp_offset = 40, fp_offset = 48, overflow_arg_area = 0x7fffffffcf80, reg_save_area = 0x7fffffffce90}}
        ap_copy = {{gp_offset = 16, fp_offset = 48, overflow_arg_area = 0x7fffffffcf80, reg_save_area = 0x7fffffffce90}}
        fd = 19
        on_2 = <value optimised out>
        list = <value optimised out>
        nlist = <value optimised out>
        cp = <value optimised out>
        written = <value optimised out>
#3  0x00007ffff6538d7a in malloc_printerr (av=0x7ffff684e1c0, bytes=<value optimised out>) at malloc.c:6283
        buf = "00000000008cfdb0"
        cp = <value optimised out>
#4  _int_malloc (av=0x7ffff684e1c0, bytes=<value optimised out>) at malloc.c:4396
        iters = <value optimised out>
        nb = 144
---Type <return> to continue, or q <return> to quit---
        idx = <value optimised out>
        bin = <value optimised out>
        victim = 0x8cfda0
        size = <value optimised out>
        victim_index = <value optimised out>
        remainder = <value optimised out>
        remainder_size = <value optimised out>
        block = <value optimised out>
        bit = <value optimised out>
        map = <value optimised out>
        fwd = <value optimised out>
        bck = 0x0
        errstr = 0x0
        __func__ = "_int_malloc"
#5  0x00007ffff653c7b4 in __libc_calloc (n=<value optimised out>, elem_size=<value optimised out>) at malloc.c:4065
        av = 0x7ffff684e1c0
        oldtop = 0x8d0370
        p = <value optimised out>
        bytes = 128
        sz = 128
        csz = <value optimised out>
        oldtopsize = 113808
        mem = <value optimised out>
        clearsize = <value optimised out>
        nclears = <value optimised out>
        d = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        hook = <value optimised out>
        __func__ = "__libc_calloc"
#6  0x00007ffff689caba in g_malloc0 (n_bytes=128) at /build/buildd/glib2.0-2.28.6/./glib/gmem.c:196
        mem = <value optimised out>
#7  0x00007ffff6b6ddea in type_node_any_new_W (pnode=0x780400, ftype=<value optimised out>, name=0x7ffff763d564 "GtkPixmap", plugin=0x0, 
    type_flags=<value optimised out>) at /build/buildd/glib2.0-2.28.6/./gobject/gtype.c:418
        n_supers = 5
        type = <value optimised out>
        node = <value optimised out>
        i = <value optimised out>
        node_size = 128
        __PRETTY_FUNCTION__ = "type_node_any_new_W"
#8  0x00007ffff6b732bd in g_type_register_static (parent_type=<value optimised out>, type_name=0x7ffff763d564 "GtkPixmap", 
    info=0x7fffffffd150, flags=0) at /build/buildd/glib2.0-2.28.6/./gobject/gtype.c:2732
        pnode = 0x780400
        node = <value optimised out>
        type = 0
        __PRETTY_FUNCTION__ = "g_type_register_static"
#9  0x00007ffff6b73358 in g_type_register_static_simple (parent_type=<value optimised out>, type_name=<value optimised out>, 
    class_size=<value optimised out>, class_init=<value optimised out>, instance_size=<value optimised out>, 
    instance_init=<value optimised out>, flags=0) at /build/buildd/glib2.0-2.28.6/./gobject/gtype.c:2685
        info = {class_size = 720, base_init = 0, base_finalize = 0, class_init = 0x7ffff7543cd0 <gtk_pixmap_class_intern_init>, 
          class_finalize = 0, class_data = 0x0, instance_size = 144, n_preallocs = 0, instance_init = 0x7ffff7543d00 <gtk_pixmap_init>, 
          value_table = 0x0}
#10 0x00007ffff7543d97 in IA__gtk_pixmap_get_type () at /build/buildd/gtk+2.0-2.24.4/gtk/gtkpixmap.c:49
        g_define_type_id = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        g_define_type_id__volatile = 0
#11 0x00007ffff75442f3 in IA__gtk_pixmap_new (val=0x8bf440, mask=0x0) at /build/buildd/gtk+2.0-2.24.4/gtk/gtkpixmap.c:85
        pixmap = <value optimised out>
        __PRETTY_FUNCTION__ = "IA__gtk_pixmap_new"
#12 0x000000000040c3af in gtk_vlabel (str=<value optimised out>) at conf_w.c:196
        layout = <value optimised out>
        st = <value optimised out>
        pm = <value optimised out>
        vs = <value optimised out>
        p = 0x8bf440
        i1 = <value optimised out>
        i2 = 0x8bbe10
        gc = 0x827470
        gc1 = 0x8bd970
        w = 24
        h = 15
        d1 = <value optimised out>
        d2 = <value optimised out>
#13 0x000000000040d571 in conf_win () at conf_w.c:607
        i = 0
        j = 0
        k = <value optimised out>
        l = <value optimised out>
        sf = <value optimised out>
        changed = <value optimised out>
        b = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        vbox = 0x83d030
        vvbox = 0x83d6f0
        box = <value optimised out>
        frame = <value optimised out>
        hbox = <value optimised out>
        nb = 0x824ae0
        n_label = <value optimised out>
        vscbar = <value optimised out>
        ctree = 0x7fffffffd390
        gname = "\240\016\264\366\377\177\000\000\301\063\213\366\377\177\000\000\210\t\264\366\377\177\000\000\266e\267\366\377\177\000\000 \bx\000\000\000\000\000\240\365j"
        gp = <value optimised out>
        obj = <value optimised out>
        obj_b = <value optimised out>
        obj2 = <value optimised out>
        cl_data = {0x0, 0x7ffff6b6b41f "H\201\304", <incomplete sequence \330>, 0x3000000018 <Address 0x3000000018 out of bounds>}
        cl_num = "\200H\202\000\000"
        rq = {width = -11408, height = 32767}
        c = 0x8cdb00
        cobj = <value optimised out>
#14 0x0000000000406036 in conf_callback (w=0x39ad, data=0x39ad) at main.c:343
        err = <value optimised out>
#15 0x00007ffff6b5081c in g_closure_invoke (closure=0x786060, return_value=0x0, n_param_values=1, param_values=0x89da80, 
    invocation_hint=0x7fffffffd540) at /build/buildd/glib2.0-2.28.6/./gobject/gclosure.c:767
        marshal = <value optimised out>
        marshal_data = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        in_marshal = 0
        __PRETTY_FUNCTION__ = "g_closure_invoke"
#16 0x00007ffff6b62019 in signal_emit_unlocked_R (node=<value optimised out>, detail=0, instance=0x780820, emission_return=0x0, 
    instance_and_params=0x89da80) at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3252
        tmp = <value optimised out>
        handler = 0x757f90
        accumulator = 0x0
        emission = {next = 0x7fffffffda40, instance = 0x780820, ihint = {signal_id = 98, detail = 0, run_type = G_SIGNAL_RUN_FIRST}, 
          state = EMISSION_RUN, chain_type = 4}
        class_closure = 0x6b9360
        handler_list = 0x757f90
        return_accu = 0x0
        accu = {g_type = 0, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, 
              v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, 
              v_pointer = 0x0}}}
        signal_id = 98
        max_sequential_handler_number = 622
        return_value_altered = 1
#17 0x00007ffff6b6b258 in g_signal_emit_valist (instance=<value optimised out>, signal_id=<value optimised out>, 
    detail=<value optimised out>, var_args=<value optimised out>) at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:2983
        instance_and_params = 0x89da80
        signal_return_type = 4
        param_values = 0x89da98
        node = 0x754760
        i = <value optimised out>
        n_params = 0
---Type <return> to continue, or q <return> to quit---
        __PRETTY_FUNCTION__ = "g_signal_emit_valist"
#18 0x00007ffff6b6b41f in g_signal_emit (instance=<value optimised out>, signal_id=<value optimised out>, detail=<value optimised out>)
    at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3040
        var_args = {{gp_offset = 24, fp_offset = 48, overflow_arg_area = 0x7fffffffd830, reg_save_area = 0x7fffffffd770}}
#19 0x00007ffff74e36ce in IA__gtk_widget_activate (widget=0x780820) at /build/buildd/gtk+2.0-2.24.4/gtk/gtkwidget.c:5019
        __PRETTY_FUNCTION__ = "IA__gtk_widget_activate"
#20 0x00007ffff73dc94d in IA__gtk_menu_shell_activate_item (menu_shell=0x77f020, menu_item=0x780820, force_deactivate=<value optimised out>)
    at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmenushell.c:1361
        slist = <value optimised out>
        shells = 0x8c05c0
        deactivate = <value optimised out>
        __PRETTY_FUNCTION__ = "IA__gtk_menu_shell_activate_item"
#21 0x00007ffff73dcce5 in gtk_menu_shell_button_release (widget=0x77f020, event=<value optimised out>)
    at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmenushell.c:788
        submenu = 0x0
        menu_item = 0x780820
        deactivate = 1
        menu_shell = 0x77f020
        priv = 0x77f150
#22 0x00007ffff73c8578 in _gtk_marshal_BOOLEAN__BOXED (closure=0x6c21a0, return_value=0x7fffffffda90, n_param_values=<value optimised out>, 
    param_values=0x8bf4d0, invocation_hint=<value optimised out>, marshal_data=<value optimised out>)
    at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmarshalers.c:86
        callback = 0x7ffff73d1420 <gtk_menu_button_release>
        cc = 0x6c21a0
        data1 = 0x77f020
        data2 = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        v_return = <value optimised out>
        __PRETTY_FUNCTION__ = "_gtk_marshal_BOOLEAN__BOXED"
#23 0x00007ffff6b5081c in g_closure_invoke (closure=0x6c21a0, return_value=0x7fffffffda90, n_param_values=2, param_values=0x8bf4d0, 
    invocation_hint=0x7fffffffda50) at /build/buildd/glib2.0-2.28.6/./gobject/gclosure.c:767
        marshal = <value optimised out>
        marshal_data = <value optimised out>
        in_marshal = 0
        __PRETTY_FUNCTION__ = "g_closure_invoke"
#24 0x00007ffff6b61e1f in signal_emit_unlocked_R (node=<value optimised out>, detail=0, instance=0x77f020, emission_return=0x7fffffffdc00, 
    instance_and_params=0x8bf4d0) at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3290
        accumulator = 0x6c2430
        emission = {next = 0x0, instance = 0x77f020, ihint = {signal_id = 34, detail = 0, run_type = G_SIGNAL_RUN_LAST}, 
          state = EMISSION_RUN, chain_type = 7672368}
        class_closure = 0x6c21a0
        handler_list = 0x0
        return_accu = 0x7fffffffda90
        accu = {g_type = 20, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, 
              v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, 
              v_pointer = 0x0}}}
        signal_id = 34
        max_sequential_handler_number = 622
        return_value_altered = 0
#25 0x00007ffff6b6afa9 in g_signal_emit_valist (instance=<value optimised out>, signal_id=<value optimised out>, 
    detail=<value optimised out>, var_args=<value optimised out>) at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:2993
        return_value = {g_type = 20, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, 
              v_double = 0, v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, 
---Type <return> to continue, or q <return> to quit---
              v_double = 0, v_pointer = 0x0}}}
        error = 0x0
        rtype = 20
        static_scope = 0
        instance_and_params = 0x8bf4d0
        signal_return_type = 20
        param_values = 0x8bf4e8
        node = 0x6c2210
        i = <value optimised out>
        n_params = 1
        __PRETTY_FUNCTION__ = "g_signal_emit_valist"
#26 0x00007ffff6b6b41f in g_signal_emit (instance=<value optimised out>, signal_id=<value optimised out>, detail=<value optimised out>)
    at /build/buildd/glib2.0-2.28.6/./gobject/gsignal.c:3040
        var_args = {{gp_offset = 32, fp_offset = 48, overflow_arg_area = 0x7fffffffdd40, reg_save_area = 0x7fffffffdc80}}
#27 0x00007ffff74e44d1 in gtk_widget_event_internal (widget=0x77f020, event=0x876ea0) at /build/buildd/gtk+2.0-2.24.4/gtk/gtkwidget.c:4988
        signal_num = <value optimised out>
        return_val = 0
#28 0x00007ffff73c6763 in IA__gtk_propagate_event (widget=0x77f020, event=0x876ea0) at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmain.c:2495
        tmp = <value optimised out>
        handled_event = <value optimised out>
        __PRETTY_FUNCTION__ = "IA__gtk_propagate_event"
#29 0x00007ffff73c6a5b in IA__gtk_main_do_event (event=0x876ea0) at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmain.c:1685
        event_widget = <value optimised out>
        grab_widget = 0x780820
        window_group = <value optimised out>
        rewritten_event = <value optimised out>
---Type <return> to continue, or q <return> to quit---
        tmp_list = <value optimised out>
        __PRETTY_FUNCTION__ = "IA__gtk_main_do_event"
#30 0x00007ffff70395cc in gdk_event_dispatch (source=<value optimised out>, callback=<value optimised out>, user_data=<value optimised out>)
    at /build/buildd/gtk+2.0-2.24.4/gdk/x11/gdkevents-x11.c:2377
        display = <value optimised out>
        event = 0x876ea0
#31 0x00007ffff6895bcd in g_main_dispatch (context=0x6a6170) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:2440
        dispatch = 0x7ffff7039580 <gdk_event_dispatch>
        was_in_call = 0
        user_data = 0x0
        callback = 0
        cb_funcs = 0x0
        cb_data = 0x0
        current_source_link = {data = 0x6a6080, next = 0x0}
        need_destroy = <value optimised out>
        source = 0x6a6080
        current = 0x86b890
        i = <value optimised out>
#32 g_main_context_dispatch (context=0x6a6170) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3013
No locals.
#33 0x00007ffff68963a8 in g_main_context_iterate (context=0x6a6170, block=<value optimised out>, dispatch=1, self=<value optimised out>)
    at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3091
        max_priority = 2147483647
        timeout = 73
        some_ready = 1
        nfds = 2
---Type <return> to continue, or q <return> to quit---
        allocated_nfds = <value optimised out>
        fds = <value optimised out>
#34 0x00007ffff68969f2 in g_main_loop_run (loop=0x6da230) at /build/buildd/glib2.0-2.28.6/./glib/gmain.c:3299
        __PRETTY_FUNCTION__ = "g_main_loop_run"
#35 0x00007ffff73c5af7 in IA__gtk_main () at /build/buildd/gtk+2.0-2.24.4/gtk/gtkmain.c:1257
        tmp_list = <value optimised out>
        functions = 0x0
        init = <value optimised out>
        loop = 0x6da230
#36 0x00000000004063fa in main (argc=1, argv=0x7fffffffe0c8) at main.c:168
        h = <value optimised out>
        i = <value optimised out>
        dirname = <value optimised out>
        cname = <value optimised out>