Fix #6750492: NPE in tablet status bar

Pull down a bugfix from BaseStatusBar.

Bug: 6750492
Change-Id: I9bd04e3a800d4dd2222844d2848208d611b60fe0
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java b/packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java
index 5cab636..f947369 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/tablet/TabletStatusBar.java
@@ -1658,6 +1658,7 @@
 
     @Override
     protected boolean isTopNotification(ViewGroup parent, NotificationData.Entry entry) {
+        if (parent == null || entry == null) return false;
         return parent.indexOfChild(entry.row) == parent.getChildCount()-1;
     }