Fix collapsing empty diff lines

What does this MR do and why?

This MR fixes a regression after !194225 (merged) that caused collapsing empty diff lines in merge requests.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Create a new merge request with a new file that only contains 3 empty lines
2. Select 'Changes' tab
3. Observe proper rendering of the diff without empty lines collapsing