Add null check before removing live tile overlay

Bug: 131630813
Change-Id: I6d2c39c61aa918b11dd3d15703fe6ca52c19778d
diff --git a/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java b/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
index afc4fcb..baac880 100644
--- a/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
+++ b/quickstep/recents_ui_overrides/src/com/android/quickstep/WindowTransformSwipeHandler.java
@@ -1062,7 +1062,9 @@
             @Override
             public void onAnimationStart(Animator animation) {
                 homeAnim.dispatchOnStart();
-                mActivity.getRootView().getOverlay().remove(mLiveTileOverlay);
+                if (mActivity != null) {
+                    mActivity.getRootView().getOverlay().remove(mLiveTileOverlay);
+                }
             }
 
             @Override