Fix NPE

Treehugger didn't hit this with the original CL (ag/9721403) but I'm
hitting it locally & believe it is the root cause of attached bug.

Test: atest NotificationManagerTest (doesn't crash)
Bug: 144947853
Bug: 144958550
Change-Id: I3a03097b1e81b81a1847ef46422a052df726eb7d
diff --git a/services/core/java/com/android/server/notification/NotificationManagerService.java b/services/core/java/com/android/server/notification/NotificationManagerService.java
index 3351bb1..3f67e7b 100755
--- a/services/core/java/com/android/server/notification/NotificationManagerService.java
+++ b/services/core/java/com/android/server/notification/NotificationManagerService.java
@@ -2055,10 +2055,10 @@
 
             @Override
             public void updateAutogroupSummary(String key, boolean needsOngoingFlag) {
-                String pkg = null;
+                String pkg;
                 synchronized (mNotificationLock) {
                     NotificationRecord r = mNotificationsByKey.get(key);
-                    pkg = r.sbn.getPackageName();
+                    pkg = r != null && r.sbn != null ? r.sbn.getPackageName() : null;
                 }
                 boolean isAppForeground = pkg != null
                         && mActivityManager.getPackageImportance(pkg) == IMPORTANCE_FOREGROUND;