monkey-proofing animation

       Bug: 5103205
       added view null check

Change-Id: I5388213e05c65c4bb644757cc999bbdf052f3c49
diff --git a/src/com/android/browser/NavTabGallery.java b/src/com/android/browser/NavTabGallery.java
index 8aa2782..af02e8d 100644
--- a/src/com/android/browser/NavTabGallery.java
+++ b/src/com/android/browser/NavTabGallery.java
@@ -127,7 +127,7 @@
     }
 
     private void animateOut(final View v, float velocity) {
-        if (mAnimator != null) return;
+        if ((v == null) || (mAnimator != null)) return;
         final int position = mFirstPosition + indexOfChild(v);
         int target = 0;
         if (velocity < 0) {