Staging gitlab-org/gitlab merge requests page is broken

Discovered in #365739 (comment 998729473) (but established not be decomposition related)

Steps to reproduce

1. Visit https://staging.gitlab.com/gitlab-org/gitlab/-/merge_requests
2. 500

https://sentry.gitlab.net/gitlab/staginggitlabcom/issues/3316743/events/81200048/ is likely related Sentry event