Fix dispatching of events when EventDispatcher is not initialized

Summary:
This diff fixes a NPE that can occur when we force the dispatching of events when the EventDispatcher is not initized.

The fix consists on avoid posting the frame callback, if the internals of EventDispatcher are not initialized yet (same behavior used by the dispatchEvent method)

Reviewed By: fkgozali

Differential Revision: D13549147

fbshipit-source-id: ef3baeb536e8772fbd83024352a37af01c21d589

ReactAndroid/src/main/java/com/facebook/react/uimanager/events/EventDispatcher.java

@@ -125,6 +125,14 @@ public void dispatchEvent(Event event) {
           event.getEventName(),
           event.getUniqueID());
     }
+    maybePostFrameCallbackFromNonUI();
+  }
+
+  public void dispatchAllEvents() {
+    maybePostFrameCallbackFromNonUI();
+  }
+
+  private void maybePostFrameCallbackFromNonUI() {
     if (mReactEventEmitter != null) {
       // If the host activity is paused, the frame callback may not be currently
       // posted. Ensure that it is so that this event gets delivered promptly.
@@ -137,10 +145,6 @@ public void dispatchEvent(Event event) {
     }
   }
 
-  public void dispatchAllEvents() {
-    mCurrentFrameCallback.maybePostFromNonUI();
-  }
-
   /**
    * Add a listener to this EventDispatcher.
    */