weather-service: free location service properly for destruction

This is needed as the location service is not properly
stopped from the portal backend if running in a sandbox
otherwise.

Signed-off-by: Markus Göllnitz <camelcasenick@bewares.it>

src/weather/gcal-weather-service.c

@@ -1203,7 +1203,7 @@ gcal_weather_service_stop (GcalWeatherService *self)
                                   (GAsyncReadyCallback) on_gclue_client_stopped_cb,
                                   self->location_service);
         }
-      self->location_service = NULL;
+      g_clear_object (&self->location_service);
     }
 
   GCAL_EXIT;