Merge 4e5bfc5 into 801bf4d

Author: lehcar09

firebase-messaging/src/main/java/com/google/firebase/messaging/SyncTask.java

@@ -191,7 +191,11 @@ public void onReceive(Context context, Intent intent) {
         Log.d(TAG, "Connectivity changed. Starting background sync.");
       }
       task.firebaseMessaging.enqueueTaskWithDelaySeconds(task, 0);
-      task.getContext().unregisterReceiver(this);
+      try {
+        task.getContext().unregisterReceiver(this);
+      } catch (IllegalArgumentException e) {
+        // The receiver is not registered
+      }
       task = null;
     }
   }