project fork URL gives 500 when not signed in

Summary

a visit to the project/forks/new URL results in a 500 error when not signed in.

Steps to reproduce

Without being signed in to gitlab, visit https://gitlab.com/gitlab-org/gitlab-ce/forks/new (or any other repository, on either self-hosted gitlab-ce or actual gitlab.com)

Expected behavior

It should allow sign-in with a redirect to back to the URL upon successful login.