With FF pinned_file enabled and only a single file there is a lot of whitespace

Problem

If you enable FF pinned_file and only have a MR with a single file the calculation seems to be off and there is a lot of whitespace:

How to reproduce

1. Enable FF echo "Feature.enable(:pinned_file)" | rails c
2. Go to a MR with only a single file change
3. Click on a line (e.g. http://gdk.test:3000/flightjs/Flight/-/merge_requests/3/diffs?pin=2d408aaa5a340d732402a346a7f915ed8a3d8a04#2d408aaa5a340d732402a346a7f915ed8a3d8a04_0_8)
4. Check the page