Bug 1964063 - Try to reset a geolocation override only if it was set before. r=saschanaz

Differential Revision: https://phabricator.services.mozilla.com/D247601

docshell/base/BrowsingContext.cpp

@@ -3254,13 +3254,12 @@ void BrowsingContext::SetGeolocationServiceOverride(
       mGeolocationServiceOverride->Init();
     }
     mGeolocationServiceOverride->Update(aGeolocationOverride.Value());
-  } else {
+  } else if (RefPtr<nsGeolocationService> serviceOverride =
+                 mGeolocationServiceOverride.forget()) {
     // Create an original service and move the locators.
     RefPtr<nsGeolocationService> service =
         nsGeolocationService::GetGeolocationService();
-    mGeolocationServiceOverride->MoveLocators(service);
-
-    mGeolocationServiceOverride = nullptr;
+    serviceOverride->MoveLocators(service);
   }
 }