ENGCOM-3784: Fixed bug, when exception occurred on order with coupons…

… cancel, made by guest after creating of customer account. #19423

 - Merge Pull Request #19423 from Winfle/magento2:fix-guest-coupon-codes-on-order-cancel
 - Merged commits:
   1. cede04f
   2. 11480e8
   3. 10fbf40
   4. 1e2f3fb
   5. 5ea6e72
   6. 9a63dad
   7. 36c2329
   8. fdf7da4

dev/tests/integration/testsuite/Magento/SalesRule/Model/Observer/AssignCouponDataAfterOrderCustomerAssignTest.php

@@ -1,4 +1,8 @@
 <?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
 
 namespace Magento\SalesRule\Model\Observer;