Edit/Delete/Block/Deactivate Ghost User, GitLab Alert Bot, or GitLab Support Bot results in 404

Summary

GitLab has a few special user accounts: Ghost User, GitLab Alert Bot, GitLab Support Bot.
They are shown in Admin Area > Users under the Without projects tab.
Clicking the Edit button for these special accounts results in a 404 error. Selecting Block, Deactivate, or Delete userfrom the cog menu also results in a404` error.

Steps to reproduce

If you don't have any of the special user accounts yet, the easiest one to create id the Ghost User. Create a normal user, and then delete it. Make sure to use Delete user instead of Delete user and contributions. When the user is deleted, a Ghost User account is created.

Go to Admin Area > Users and select the Without projects tab.
Click the Edit button for these Ghost User account.

What is the current bug behavior?

A 404 error page is shown.

What is the expected correct behavior?

These special user accounts can't be edited, deleted, blocker, or decativated, so these actions should not be shown for these accounts.

Relevant logs and/or screenshots

(Paste any relevant logs - please use code blocks (```) to format console output, logs, and code as it's tough to read otherwise.)

Application info

Fresh Docker install of GitLab EE 12.6.2