Check null values in shouldAnimate

Summary:
Looks like there could be cases when the NativeHirearchyManager may be asking if it should animate on a view that has been removed. Adding a null check

Changelog:
[General] [Fixed] - Check null values in shouldAnimate

Reviewed By: makovkastar

Differential Revision: D20063054

fbshipit-source-id: 5b3b1c27b9aba57a592bd8d4e27a970cf0912b5d

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

@@ -88,6 +88,9 @@ public class LayoutAnimationController {
     // 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;
   }