Setting assignee is from boards is cancelled when you click outside the sidebar
I'm having the issues for group board (Self-hosted GitLab Enterprise Edition 11.10.4-ee). Sub-problem of gitlab-ee#11021, ping @smcgivern.
Steps to reproduce
- On sidebar, click Assignee:Edit
- click someone from list
- Click anywhere on list that the issue you're currently editing belongs to
- Changes to assignees won't be applied
- If you click on any other list, the changes will be applied