Critical messages when bluetooth panel is closed while being initialized

Steps to reproduce:

1. Open GNOME Terminal
2. Run gnome-control-center bluetooth
3. Close GNOME Control Center
4. Run gnome-control-center wifi

I get the following critical messages:

(gnome-control-center:11073): GLib-GIO-CRITICAL **: 16:09:07.839: g_dbus_connection_call_internal: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
(gnome-control-center:11073): GLib-GIO-CRITICAL **: 16:09:07.839: g_dbus_connection_unregister_object: assertion 'G_IS_DBUS_CONNECTION (connection)' failed
(gnome-control-center:11073): GLib-GIO-CRITICAL **: 16:09:07.839: g_bus_unwatch_name: assertion 'watcher_id > 0' failed