“Something has gone terribly wrong” on pull request from deleted branch (BB-6129)

On https://bitbucket.org/OpenUru_org/cwe-ou/pull-request/18 I get an error message “Oops! Something has gone terribly wrong...” on all three tabs (Diff/Commits/Activity). In particular, I can no longer see the discussion that happened on this pull request, which makes me a bit queasy, because those discussions are important information regarding traceability of the development of the project. The participants icons at the top right still show the involved people though, so I’m hopeful that no data has been lost.

The problem appeared with the new site design, in the old design the discussion was visible.

It most likely has something to do with the fact that the source branch of this pull request was mistakenly deleted by its owner a while ago. I’m also not sure why the pull request is marked “declined” (though that may not be Bitbucket’s fault), as far as I am concerned it is open and will be accepted soon.

(As as side note, I would also consider it a bug that the commits disappeared from the pull request when they were removed from the source repository. In my opinion, the pull request should keep a reference to them, no matter whether they are still present in the source repository. But that already happened in the old design and is not part of this bug report.)