Fix definition of NativeAnimated.isEmpty

Summary:
Noticed in D36098912 (https://github.com/facebook/react-native/commit/5de0f145eca36d3263cb8a9928add278cdfffa2b) that the definition of NativeAnimatedModule's OperationQueue.isEmpty was incorrect as it didn't account for `mPeekedOperation`, while `drainQueueIntoList`  did.

Changelog: [Internal]

Reviewed By: mdvacca

Differential Revision: D36109810

fbshipit-source-id: afd7059975ce6e5c65d1975d168a03f0881bd7c1

ReactAndroid/src/main/java/com/facebook/react/animated/NativeAnimatedModule.java

@@ -113,7 +113,7 @@ public class NativeAnimatedModule extends NativeAnimatedModuleSpec
 
     @AnyThread
     boolean isEmpty() {
-      return mQueue.isEmpty();
+      return mQueue.isEmpty() && mPeekedOperation != null;
     }
 
     void setSynchronizedAccess(boolean isSynchronizedAccess) {
@@ -150,7 +150,7 @@ public class NativeAnimatedModule extends NativeAnimatedModuleSpec
 
     @UiThread
     private @Nullable List<UIThreadOperation> drainQueueIntoList(long maxBatchNumber) {
-      if (mQueue.isEmpty() && mPeekedOperation == null) {
+      if (isEmpty()) {
         return null;
       }