Pull model: skip transaction notifications after FabricUIManager is invalidated

onTransactionAvailable kept no binding check after the queued pull mount item was
replaced by pending surfaces, so a notification arriving after invalidate() still
marked the surface pending and armed a frame whose pull does nothing. Return early
when the binding is gone, as before.

Author: bartlomiejbloniarz

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java

@@ -1065,6 +1065,9 @@ public void runGuarded() {
   @ThreadConfined(ANY)
   @VisibleForTesting
   void onTransactionAvailable(int surfaceId) {
+    if (mBinding == null) {
+      return;
+    }
     mMountItemDispatcher.addSurfaceIdToPull(surfaceId);
     if (UiThreadUtil.isOnUiThread()) {
       mMountItemDispatcher.tryDispatchMountItems();