Fix validation error from backend not showing on failed import

What does this MR do and why?

Fix validation error from backend not showing immediately on failed Direct transfer import.

Changelog: fixed

Screenshots or screen recordings

Before	After
Direct_transfer_validation_error_before	Direct_transfer_validation_error_after

How to set up and validate locally

1. In the header bar, click on + icon (Create new...) > New group.
2. Select Import group.
3. Fill in the GDK URL as GitLab source instance URL and a Person Access Token.
4. You should be on the Import groups page.
5. Start a new import for any group with the New group name ending with underscore _ (which is invalid input).

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #404982 (closed)