Comment 2 for bug 855549

StacktraceTop:
 g_type_check_instance_cast (type_instance=0xa7b280, iface_type=10980880) at /build/buildd/glib2.0-2.29.92/./gobject/gtype.c:3985
 device_changed (device=0x9a6c30, property=0xc24b90 "Connected", value=0xc3c090, user_data=0xa7b280) at bluetooth-client.c:384
 marshal_dbus_message_to_g_marshaller (closure=0xabe1f0, return_value=0x0, n_param_values=<optimized out>, param_values=<optimized out>, invocation_hint=0x7fff882740a0, marshal_data=0x0) at dbus-gproxy.c:1733
 g_closure_invoke (closure=0xabe1f0, return_value=0x0, n_param_values=3, param_values=0xa4f190, invocation_hint=<optimized out>) at /build/buildd/glib2.0-2.29.92/./gobject/gclosure.c:774
 signal_emit_unlocked_R (node=<optimized out>, detail=1867, instance=0x9a6c30, emission_return=0x0, instance_and_params=0xa4f190) at /build/buildd/glib2.0-2.29.92/./gobject/gsignal.c:3272