Fix layout animation crash

Summary: As of D14529038, LayoutAnimations can sometimes throw an exception due to the view being null.  This can happen when elements are removed/added and is not fixable in product code. This is a temporary fix - the root cause for this issue will be fixed soon.

Reviewed By: lunaleaps

Differential Revision: D15428791

fbshipit-source-id: 41200e572ed7d5d470754792c5576a0ea23fe946

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

@@ -444,7 +444,7 @@ public class NativeViewHierarchyManager {
             arrayContains(tagsToDelete, viewToRemove.getId())) {
           // The view will be removed and dropped by the 'delete' layout animation
           // instead, so do nothing
-        } else {
+        } else if (viewToManage != null) {
           viewManager.removeViewAt(viewToManage, normalizedIndexToRemove);
         }
 

ReactAndroid/src/main/java/com/facebook/react/uimanager/layoutanimation/LayoutAnimationController.java

@@ -82,10 +82,14 @@ public class LayoutAnimationController {
   }
 
   public boolean shouldAnimateLayout(View viewToAnimate) {
-    // if view parent is null, skip animation: view have been clipped, we don't want animation to
-    // resume when view is re-attached to parent, which is the standard android animation behavior.
-    // If there's a layout handling animation going on, it should be animated nonetheless since the
-    // ongoing animation needs to be updated.
+    // if view is null or the view parent is null, skip animation: view have been clipped,
+    // we don't want animation to resume when view is re-attached to parent, which is the
+    // standard android animation behavior. If there's a layout handling animation going on,
+    // it should be animated nonetheless since the ongoing animation needs to be updated.
+
+    if (viewToAnimate == null) {
+      return false;
+    }
     return (mShouldAnimateLayout && viewToAnimate.getParent() != null)
       || mLayoutHandlers.get(viewToAnimate.getId()) != null;
   }

ReactAndroid/src/main/java/com/facebook/react/views/view/ReactViewGroup.java

@@ -465,7 +465,9 @@ public class ReactViewGroup extends ViewGroup implements
     mDrawingOrderHelper.handleRemoveView(getChildAt(index));
     setChildrenDrawingOrderEnabled(mDrawingOrderHelper.shouldEnableCustomDrawingOrder());
 
-    super.removeViewAt(index);
+    if (getChildAt(index) != null) {
+      super.removeViewAt(index);
+    }
   }
 
   @Override