Keyboard navigation between diffs is not working properly while viewing a trimmed file

[AlexandraMoga]

Similar to #967 but for diffs

Describe the problem and steps to reproduce it:

1. Load the following compare page: https://code.addons-dev.allizom.org/en-US/compare/1865/versions/1688304...1688388/?path=lib%2Fadblockplus.js
2. Press n on your keyboard to jump to the next changed diff
3. Press n again and notice the line number displayed in the URL

What happened?

The URL shows the next diff with changes while the UI doesn't update

What did you expect to happen?

The UI should display the correct diff when using keyboard navigation while viewing a trimmed file

Anything else we should know?

• if you opt to see the original file, the issue will not reproduce

┆Issue is synchronized with this Jira Task

[kumar303]

Thanks for filing. This is similar to https://github.com/mozilla/addons-code-manager/issues/967 but different.