Comment 2 for bug 830029

StacktraceTop:
 g_closure_invoke (closure=0x8ca3b98, return_value=0x0, n_param_values=2, param_values=0x9903ec8, invocation_hint=0xbf6c80f0) at /build/buildd/glib2.0-2.29.16/./gobject/gclosure.c:748
 signal_emit_unlocked_R (node=0x8caa9b8, detail=0, instance=0x8e49008, emission_return=0x0, instance_and_params=0x9903ec8) at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3201
 g_signal_emit_valist (instance=0x8e49008, signal_id=18, detail=0, var_args=0xbf6c82a0 "\304\205l\277\346e\352") at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3002
 g_signal_emit (instance=0x8e49008, signal_id=18, detail=0) at /build/buildd/glib2.0-2.29.16/./gobject/gsignal.c:3059
 _gtk_widget_grab_notify (widget=0x8e49008, was_grabbed=0) at /build/buildd/gtk+3.0-3.1.12/./gtk/gtkwidget.c:6382