"Start a review" fails on discussion started on a commit
Summary
If I try to start a review on a discussion that was started on a commit I'm unable to post a comment. The comment field disappears as it does when a comment is successful, but the comment doesn't appear. DevTools shows that a request to drafts returns status 500
Steps to reproduce
Attempt to start a review on a discussion that was started on a commit. E.g., this one started by GitLab Bot: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/7368?commit_id=da53a0d72d2ca69b4b89c59e57bcff22ef63540c#note_109984161
What is the current bug behavior?
- The comment field disappears but the comment doesn't appear.
- If I click on the input field again the comment reappears, unsubmitted
- The UI makes a call to
draftsthat returns a status 500 error
What is the expected correct behavior?
A review is started
Output of checks
This bug happens on GitLab.com