Fix code unfold not working on Compare commits page

### What does this MR do?

The code unfold buttons (`...`) don't work when you go to Commits -> Compare mode. This MR fixes that.

### Are there points in the code the reviewer needs to double check?

Check to make sure all the right initializers are run in the `projects:compare:xxx` case. I'm also not sure if there are other cases where a diff is shown but the code unfolding is not activated.

### What are the relevant issue numbers / [Feature requests](http://feedback.gitlab.com/)?

Closes #1274

See merge request !434