Merge commit SHA not showing in merge request widget
### Summary
When a merge request is merged, a merge commit is created and the SHA shown in the merge request widget.
### Steps to reproduce
Not sure, visit gitlab-ce!22193 and you will see that the link to the commit is missing.
Looking at gitlab-ce!22030 it seems to have the SHA as expected.
Only difference I see is that gitlab-ce!22193 still has the source branch available.
### Example Project
gitlab-ce!22193
### What is the current *bug* behavior?
Commit link is not shown, but the user still can copy the copy SHA button
### What is the expected *correct* behavior?
Show SHA link.
### Relevant logs and/or screenshots

### Output of checks
This bug happens on GitLab.com
issue