Check that a transaction is opened before closing it

chrome/browser/ui/cocoa/notifications/xpc_transaction_handler.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <AppKit/AppKit.h>
 #import <Foundation/Foundation.h>
 
 #import "chrome/browser/ui/cocoa/notifications/xpc_transaction_handler.h"
 
 @class NSUserNotificationCenter;
@@ skipping 17 matching lines @@
     xpc_transaction_begin();
     transactionOpen_ = true;
   }
 }
 
 - (void)closeTransactionIfNeeded {
   @synchronized(self) {
     NSUserNotificationCenter* notificationCenter =
         [NSUserNotificationCenter defaultUserNotificationCenter];
     NSUInteger showing = [[notificationCenter deliveredNotifications] count];
-    if (showing == 0) {
+    if (showing == 0 && transactionOpen_) {
       xpc_transaction_end();
       transactionOpen_ = false;
     }
   }
 }
 @end