Merge request dicussion diff wrong hostname

Summary

The hostname of the hyperlink to the diff of the change inside a discussion is without the custom port.

Steps to reproduce

• Setup GitLab with custom port (e.g. 1443 for 443 (HTTPS))
• Create a merge request
• Open a discussion
• Change the code which concerns the code in the discussion
• Click on the version X of the diff of the <USER> changed this line in version X of the diff YZ minutes ago after the command
• The custom port of the hyperlink is missing

https://hostname/group/project/merge_requests/86/diffs?diff_id=315&start_sha=66f1333c2890d44fdd32ada5744abdae04437a73#75e9df95f77437301dd6a6d0944b44323cec5de3_101_102

should be

https://hostname:1443/group/project/merge_requests/86/diffs?diff_id=315&start_sha=66f1333c2890d44fdd32ada5744abdae04437a73#75e9df95f77437301dd6a6d0944b44323cec5de3_101_102

What is the current bug behavior?

Error: Network timeout -> hostname under 443 not reachable

What is the expected correct behavior?

The view of the diff.