Fixed an issue where HUNS could have a background

am: 1791f50134

Change-Id: Ia48513df95a24d69d755684c50c6730e56b6b100

packages/SystemUI/src/com/android/systemui/statusbar/stack/NotificationStackScrollLayout.java

@@ -2002,6 +2002,7 @@ public class NotificationStackScrollLayout extends ViewGroup
         if (!mIsExpanded) {
             mBackgroundBounds.top = 0;
             mBackgroundBounds.bottom = 0;
+            return;
         }
         ActivatableNotificationView firstView = mFirstVisibleBackgroundChild;
         int top = 0;