Setting unused shadow to null

Change-Id: I1122cd9b6b01c18b2393ad6eb2dbc50b0460f78b

src/com/android/launcher3/BaseRecyclerViewFastScrollPopup.java

@@ -119,6 +119,7 @@ public class BaseRecyclerViewFastScrollPopup {
             mShadow = HolographicOutlineHelper.obtain(
                     mRv.getContext()).createMediumDropShadow(mBg, false /* shouldCache */);
         } else {
+            mShadow = null;
             mBgBounds.setEmpty();
         }