Okay here is more helpful backtrace captured at the moment I get a property update for the volume key which is not of the expected gdouble type but instead NULL.


Breakpoint 1, volume_widget_property_update (item=0x98c26a8, 
    property=0x990fdb0 "x-canonical-ido-volume-level", value=0x0, userdata=0x9a003a0)
    at volume-widget.c:137
137	      g_debug ("where are you coming from");
(gdb) bt
#0  volume_widget_property_update (item=0x98c26a8, property=0x990fdb0 "x-canonical-ido-volume-level", 
    value=0x0, userdata=0x9a003a0) at volume-widget.c:137
#1  0x02eb620f in _dbusmenu_menuitem_marshal_VOID__STRING_VARIANT (closure=0x99fdd78, 
    return_value=0x0, n_param_values=3, param_values=0x9c5f908, invocation_hint=0xbf947060, 
    marshal_data=0x0) at ../../libdbusmenu-glib/menuitem-marshal.c:83
#2  0x007b0372 in g_closure_invoke (closure=0x99fdd78, return_value=0x0, n_param_values=3, 
    param_values=0x9c5f908, invocation_hint=0xbf947060)
    at /build/buildd/glib2.0-2.28.4/./gobject/gclosure.c:767
#3  0x007c3048 in signal_emit_unlocked_R (node=0x99ac6c8, detail=0, instance=0x98c26a8, 
    emission_return=0x0, instance_and_params=0x9c5f908)
    at /build/buildd/glib2.0-2.28.4/./gobject/gsignal.c:3252
#4  0x007cbb29 in g_signal_emit_valist (instance=0x98c26a8, signal_id=225, detail=0, 
    var_args=0xbf947224 "\001") at /build/buildd/glib2.0-2.28.4/./gobject/gsignal.c:2983
#5  0x007cbcc2 in g_signal_emit (instance=0x98c26a8, signal_id=225, detail=0)
    at /build/buildd/glib2.0-2.28.4/./gobject/gsignal.c:3040
#6  0x02eb441b in dbusmenu_menuitem_property_set_variant (mi=0x98c26a8, 
    property=0x99eb830 "x-canonical-ido-volume-level", value=<value optimised out>)
    at ../../libdbusmenu-glib/menuitem.c:1239
#7  0x02eb5110 in dbusmenu_menuitem_property_remove (mi=0x98c26a8, 
    property=0x99eb830 "x-canonical-ido-volume-level") at ../../libdbusmenu-glib/menuitem.c:1400
#8  0x02ebbb6a in menuitem_get_properties_replace_cb (properties=0x9b63b00, error=0x0, data=0x98c26a8)
    at ../../libdbusmenu-glib/client.c:1375
#9  0x02ebb693 in get_properties_callback (obj=0x99b99a8, res=0x9a74608, user_data=0xb4955100)
    at ../../libdbusmenu-glib/client.c:626
#10 0x00678cbf in g_simple_async_result_complete (simple=0x9a74608)
---Type <return> to continue, or q <return> to quit---
    at /build/buildd/glib2.0-2.28.4/./gio/gsimpleasyncresult.c:747
#11 0x006cecc1 in reply_cb (connection=0x98b1010, res=0x9ac7918, user_data=0x9a74608)
    at /build/buildd/glib2.0-2.28.4/./gio/gdbusproxy.c:2158
#12 0x00678cbf in g_simple_async_result_complete (simple=0x9ac7918)
    at /build/buildd/glib2.0-2.28.4/./gio/gsimpleasyncresult.c:747
#13 0x006c3d03 in g_dbus_connection_call_done (source=0x98b1010, result=0x9a66f50, 
    user_data=0x9c22d30) at /build/buildd/glib2.0-2.28.4/./gio/gdbusconnection.c:4998
#14 0x00678cbf in g_simple_async_result_complete (simple=0x9a66f50)
    at /build/buildd/glib2.0-2.28.4/./gio/gsimpleasyncresult.c:747
#15 0x00678ddd in complete_in_idle_cb (data=0x9a66f50)
    at /build/buildd/glib2.0-2.28.4/./gio/gsimpleasyncresult.c:757
#16 0x00a66311 in g_idle_dispatch (source=0x9ca9388, callback=0x678dc0 <complete_in_idle_cb>, 
    user_data=0x9a66f50) at /build/buildd/glib2.0-2.28.4/./glib/gmain.c:4545
#17 0x00a6aaa8 in g_main_dispatch (context=0x98551c8)
    at /build/buildd/glib2.0-2.28.4/./glib/gmain.c:2440
#18 g_main_context_dispatch (context=0x98551c8) at /build/buildd/glib2.0-2.28.4/./glib/gmain.c:3013
#19 0x00a6b270 in g_main_context_iterate (context=0x98551c8, block=10991648, dispatch=1, 
    self=<value optimised out>) at /build/buildd/glib2.0-2.28.4/./glib/gmain.c:3091
#20 0x00a6b92b in g_main_loop_run (loop=0x99ca5c0) at /build/buildd/glib2.0-2.28.4/./glib/gmain.c:3299
#21 0x00242b99 in gtk_main () from /usr/lib/libgtk-x11-2.0.so.0
#22 0x0804d426 in main ()