Visit a project with only `issues` feature on will get HTTP 500 error

Summary

• Visit a project with only issues feature on will get HTTP 500 error.
• gitlab.com with edition GitLab Enterprise Edition 9.0.0-rc2-ee 81207b0.

Steps to reproduce

1. setup a project with only issues feature on.

2. visit the project in browser and get 500 error.

What is the current bug behavior?

Visit project url, fetch HTTP 500 error.

What is the expected correct behavior?

Visit project url, fetch correct page.

Relevant logs and/or screenshots

See above.

Output of checks

This bug happens on GitLab.com with edition GitLab Enterprise Edition 9.0.0-rc2-ee 81207b0.

Results of GitLab environment info

Unavailable.

Results of GitLab application Check

Unavailable.

Possible fixes

None sense of it.