Make sure no callbacks are called when GoogleMap is destroyed

We faced an IllegalStateException related to a null root view of
a fragment layout.

If the GoogleMap is destroyed, there is no need to call the callbacks
related to it in an upcoming future.

play-services-maps-core-mapbox/src/main/kotlin/org/microg/gms/maps/mapbox/GoogleMap.kt

@@ -804,6 +804,7 @@ class GoogleMapImpl(context: Context, var options: GoogleMapOptions) : AbstractG
     override fun onPause() = mapView?.onPause() ?: Unit
     override fun onDestroy() {
         Log.d(TAG, "destroy");
+        userOnInitializedCallbackList.clear()
         lineManager?.onDestroy()
         lineManager = null
         fillManager?.onDestroy()