Fityk crashes when using menuproxy

[Marcin Wojdyr]

I'm upstream developer of fityk and I've got several reports from Ubuntu 14.04 users that the program crashes when using Unity. The workaround is to set UBUNTU_MENUPROXY=0.
To reproduce:
apt-get install fityk
fityk
and zoom in using a mouse.

Valgrind shows this:
==16000== Invalid read of size 1
==16000== at 0x8B39FE0: g_str_hash (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4002.0)
==16000== by 0x8B3903F: ??? (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4002.0)
==16000== by 0xFD9B161: ??? (in /usr/lib/x86_64-linux-gnu/libunity-gtk2-parser.so.0.0.0)
==16000== by 0xFD948E1: ??? (in /usr/lib/x86_64-linux-gnu/libunity-gtk2-parser.so.0.0.0)
==16000== by 0xFD966AC: ??? (in /usr/lib/x86_64-linux-gnu/libunity-gtk2-parser.so.0.0.0)
==16000== by 0x88C03B7: g_closure_invoke (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x88D1D3C: ??? (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x88D9A28: g_signal_emit_valist (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x88D9CE1: g_signal_emit (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x88C4724: ??? (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x88C6CEA: g_object_notify (in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0.4002.0)
==16000== by 0x7D96DD4: gtk_widget_show (in /usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0.2400.23)
==16000== Address 0x0 is not stack'd, malloc'd or (recently) free'd
==16000==
==16000==
==16000== Process terminating with default action of signal 11 (SIGSEGV)
==16000== Access not within mapped region at address 0x0
==16000== at 0x8B39FE0: g_str_hash (in /lib/x86_64-linux-gnu/libglib-2.0.so.0.4002.0)
(the same traceback again)

The program creates radio item in a submenu, later deletes it and creates a new radio item in the same place - and segfaults at this point.