Comment 2 for bug 804195

StacktraceTop:
 do_user_switch (button=0x93c3b10, plug=0x93bc060) at gs-lock-plug.c:171
 switch_user_button_clicked (button=0x93c3b10, plug=0x93bc060) at gs-lock-plug.c:1456
 g_cclosure_marshal_VOID__VOID (closure=0x9406528, return_value=0x0, n_param_values=1, param_values=0x94485c0, invocation_hint=0xbf8c40d0, marshal_data=0x0) at /build/buildd/glib2.0-2.29.8/./gobject/gmarshal.c:79
 g_closure_invoke (closure=0x9406528, return_value=0x0, n_param_values=1, param_values=0x94485c0, invocation_hint=0xbf8c40d0) at /build/buildd/glib2.0-2.29.8/./gobject/gclosure.c:771
 signal_emit_unlocked_R (node=0x93af520, detail=0, instance=0x93c3b10, emission_return=0x0, instance_and_params=0x94485c0) at /build/buildd/glib2.0-2.29.8/./gobject/gsignal.c:3256