When submitting a new Pull Request leaving the title empty the reviewers added to it disappear

Summary

When creating a new Pull Request, if you delete the auto-populated title, add reviewers to it, and submit the form, the Pull Request screen will reload due to the missing title and the reviewers previously added will be removed.

Steps to Reproduce

1. Go to the Pull Request creation screen
2. Delete the Pull Request title
3. Add a few users as reviewers
4. Click Create to make the Pull Request creation screen reload with an error in the title.
5. Note that the reviewers previously added are now missing

Expected Results

Users added as reviewers should remain being displayed as such when the page reloads with an error in the title.

Actual Results

Users added as reviewers are removed when the page reloads.

Workaround

None