Change the order of handling exception and clearing react instance manager

Summary:
Changelog: [Internal]
Added better explanation to help debugging ViewManager crashes

Reviewed By: makovkastar

Differential Revision: D24539229

fbshipit-source-id: 36a010324cbf29dfe63784682715b963394a87fb

ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewManagerRegistry.java

@@ -56,7 +56,11 @@ public final class ViewManagerRegistry {
     if (mViewManagerResolver != null) {
       viewManager = getViewManagerFromResolver(className);
       if (viewManager != null) return viewManager;
-      throw new IllegalViewOperationException("ViewManagerResolver returned null for " + className);
+      throw new IllegalViewOperationException(
+          "ViewManagerResolver returned null for "
+              + className
+              + ", existing names are: "
+              + mViewManagerResolver.getViewManagerNames());
     }
     throw new IllegalViewOperationException("No ViewManager found for class " + className);
   }