Showing an error when order refund fails

[dparker1005]

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• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

When an order refund fails on the Edit Member "memberships" tab, show an error message and halt any other changes.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully run tests with your changes locally?

Changelog entry

Enter a summary of all changes on this Pull Request. This will appear in the changelog if accepted.

[kimcoleman]

Tested and working great. My only holdup right now is the language. Syncing with @ideadude today to get this approved.