### Summary In `gitlab-insights` and future features we rely on the `merged_at` timestamp being available for Merge Requests in the `merged` state. Under certain circumstances this field isn't available for merged MRs when indexing MRs and retrieving and individual MR via the API. This definitely does not affect all MRs, but I could not notice a pattern between those affected ### Steps to reproduce - Query `api/v4/projects/:project_id/merge_requests` - Notice some MRs do not have `merged_at` data available ### Example Project The following merged MR is an example that exhibits the problem: * https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24137 * https://gitlab.com/api/v4/projects/gitlab-org%2Fgitlab-ce/merge_requests/24137 ### What is the current *bug* behavior? - `merged_at` field is `null` ### What is the expected *correct* behavior? - `merged_at` field should be populated with the relevant timestamp ### Relevant logs and/or screenshots N/A ### Output of checks This bug happens on GitLab.com #### Results of GitLab environment info gitlab-ce~3293941 `v11.8.0-rc9` ### Possible fixes (If you can, link to the line of code that might be responsible for the problem)