Sorry, here's the complete backtrace:

#0  0x00007ffff56bae8c in g_type_check_instance_cast ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#1  0x00007fffd8366cbb in ?? ()
   from /usr/lib/x86_64-linux-gnu/libdbusmenu-gtk.so.4
#2  0x00007ffff5698300 in g_closure_invoke ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#3  0x00007ffff56aa370 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4  0x00007ffff56b2601 in g_signal_emit_valist ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5  0x00007ffff56b2852 in g_signal_emit ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6  0x00007ffff569ce35 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#7  0x00007ffff569c83e in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#8  0x00007ffff569eaa3 in g_object_thaw_notify ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#9  0x00007ffff66ad3e4 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#10 0x00007ffff65cbe21 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#11 0x00007ffff56b7b36 in g_type_class_ref ()
---Type <return> to continue, or q <return> to quit---
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#12 0x00007ffff569f301 in g_object_newv ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#13 0x00007ffff569f89c in g_object_new ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#14 0x00005555555c1b10 in pidgin_conv_setup_quickfind (
    container=0x55555595bd30, gtkconv=0x5555566e3730)
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkconv.c:4912
#15 setup_common_pane (gtkconv=0x5555566e3730)
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkconv.c:5061
#16 private_gtkconv_new (conv=conv@entry=0x5555566839d0, hidden=hidden@entry=0)
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkconv.c:5368
#17 0x00005555555c2a7b in pidgin_conv_new (conv=0x5555566839d0)
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkconv.c:5474
#18 0x00007ffff50bd07d in purple_conversation_new (
    type=type@entry=PURPLE_CONV_TYPE_IM, account=account@entry=0x55555593ed30, 
    name=name@entry=0x555555ca1a10 "<email address hidden>")
    at /build/buildd/pidgin-2.10.6/./libpurple/conversation.c:450
#19 0x00005555555c7060 in pidgin_dialogs_im_with_user (account=0x55555593ed30, 
    username=0x555555ca1a10 "<email address hidden>")
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkdialogs.c:899
#20 0x000055555559ae3a in gtk_blist_row_activated_cb (tv=<optimized out>, 
    path=<optimized out>, col=<optimized out>, data=<optimized out>)
---Type <return> to continue, or q <return> to quit---
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkblist.c:1228
#21 0x00007ffff5698300 in g_closure_invoke ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#22 0x00007ffff56aa370 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#23 0x00007ffff56b2601 in g_signal_emit_valist ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#24 0x00007ffff56b2852 in g_signal_emit ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#25 0x00007ffff67429bd in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#26 0x00007ffff6642719 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#27 0x00007ffff5698300 in g_closure_invoke ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#28 0x00007ffff56aa0f0 in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#29 0x00007ffff56b1d7a in g_signal_emit_valist ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#30 0x00007ffff56b2852 in g_signal_emit ()
   from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0
#31 0x00007ffff675bb0e in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
---Type <return> to continue, or q <return> to quit---
#32 0x00007ffff6640ab4 in gtk_propagate_event ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#33 0x00007ffff6640e0b in gtk_main_do_event ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#34 0x00007ffff62b5d7c in ?? ()
   from /usr/lib/x86_64-linux-gnu/libgdk-x11-2.0.so.0
#35 0x00007ffff53d8bb5 in g_main_context_dispatch ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#36 0x00007ffff53d8ee8 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#37 0x00007ffff53d92e2 in g_main_loop_run ()
   from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#38 0x00007ffff663fdf7 in gtk_main ()
   from /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0
#39 0x000055555558f0e9 in main (argc=1, argv=0x7fffffffe2b8)
    at /build/buildd/pidgin-2.10.6/./pidgin/gtkmain.c:933