### Summary (Summarize the bug encountered concisely) Starting a discussion in the main thread of a MR (not on a diff) and marking it as resolved doesn't present the "Toggle discussion" button. ### Steps to reproduce - Create new project - Create MR - Start discussion in main discussion tab ### Example Project - https://gitlab.com/issue-reproduce/mr-discussion-collapse/merge_requests/1 ### What is the current *bug* behavior? Discussion cannot be collapsed like a diff discussion ### What is the expected *correct* behavior? Discussion can be collapsed like a diff discussion ### Output of checks This bug happens on GitLab.com #### Results of GitLab environment info gitlab-ce~3293941 `v11.9.0-rc9` #### Results of GitLab application Check gitlab-ce~3293941 `v11.9.0-rc9` ### Possible fixes (If you can, link to the line of code that might be responsible for the problem)