Check if the allocated views set for exists for surface on mount

Summary:
Adds a check to verify that we are not trying to insert a new view id into a non-existent set.

Changelog: [Internal]

Reviewed By: sammy-SC

Differential Revision: D33621031

fbshipit-source-id: 8468af69bea250a70d656789ea819c39b55a9de6

ReactAndroid/src/main/java/com/facebook/react/fabric/jni/FabricMountingManager.cpp

@@ -413,7 +413,8 @@ void FabricMountingManager::executeMount(
       }
     }
 
-    if (shouldRememberAllocatedViews_) {
+    if (shouldRememberAllocatedViews_ &&
+        allocatedViewsIterator != allocatedViewRegistry_.end()) {
       auto &views = allocatedViewsIterator->second;
       for (auto const &mutation : mutations) {
         switch (mutation.type) {