Specifying author/assignee in issuable search bar causes a warning message for an anonymous user

Summary

Only when specifying author and/or assignee in issuable search bar (Project Issues or Project Milestones), anonymous user will see a warning message.

Steps to reproduce

1. Logged out from the GitLab if you logged in.
2. Access to a page with the issuable search bar such as Project Issues or Project Milestones. e.g.:
   • https://gitlab.com/gitlab-org/gitlab-ce/issues?author_username=tnir
   • https://gitlab.com/gitlab-org/gitlab-ce/merge_requests?author_username=tnir

What is the current bug behavior?

You can see You need to be logged in warning while probably you are very new to GitLab or you do not want to log in.

What is the expected correct behavior?

Suppress the warning message and just stop to stylize people (author/assignee) the issuable search bar.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com (since 9.3).

/label bug, regression (!11402 (merged)), issues, milestones, frontend