Merge Requests filter is broken on gitlab.com

Summary

When attempting to filter by Target-Branch on Merge requests, the dropdown menu for branches is broken, reporting "An error occurred fetching the dropdown data"

Steps to reproduce

Go to project merge requests, in the search bar, choose "Target-Branch" then "=" and then a dropdown should appear with branches.

What is the current bug behavior?

Error occurs and dev console reports a 404 error for:

https://gitlab.com/autocomplete/merge_request_target_branches.json?group_id=&project_id=

What is the expected correct behavior?

Expect to see a dropdown list of branches

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com