Unable to use project with dot as project slug

Summary

An user is unable to use a project with only a dot (".") as project slug. The project is created but not accessable, because it's always mapped to the user profile or group.

Steps to reproduce

Create a project with any name and a dot as project slug.

Example Project

Not applicable.

What is the current bug behavior?

A project is created, but not accessable. The project is not deletable in the admin menu, only via the GitLab Api.

What is the expected correct behavior?

The "." should either an incorrect project slug or correctly mapped to the project.

Scope

This bug is at least present in the current gitlab.com instance and GitLab CE 11.5.4.