[forwardport] Resolves 6731 by adding a custom message for refunding shipping

[gelanivishal]

Original Pull Request

#18844

Description (*)

Fixed Issues (if relevant)

1. 'Exception' with message 'Warning: Division by zero in vendor/magento/module-sales/Model/Order/Creditmemo/Total/Discount.php on line 32' in vendor/magento/framework/App/ErrorHandler.php:61 #6731: 'Exception' with message 'Warning: Division by zero in vendor/magento/module-sales/Model/Order/Creditmemo/Total/Discount.php on line 32' in vendor/magento/framework/App/ErrorHandler.php:61

Manual testing scenarios (*)

1. Create a order with free shipment
2. Invoice the order
3. Create new creditmemo
4. Refund $10 in Refund Shipping

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[magento-engcom-team]

Hi @gelanivishal. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

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[magento-engcom-team]

Hi @VladimirZaets, thank you for the review.
ENGCOM-3369 has been created to process this Pull Request

[VladimirZaets]

Hi @gelanivishal. We can't reproduce this issue on the 2.3-develop branch. Please provide more details. Thanks

[sidolov]

Hi @gelanivishal , I am closing this PR now due to inactivity.
Please reopen and update if you wish to continue.
Thank you for the collaboration!