Track selector list, clicking to show a track makes the mouse hover highlight disappear

In the track selector list, move the mouse to a track, it gets highlighted.
Go to an already visible track (with the tick) and click, the tick disappear, but the highlight stays -- This is good, it shows where the cursor points to, and allows going up/down with the arrow keys if preferred.

However, go to a hidden track (no tick) and click, the tick is added, but the highlight goes away! This is a bit confusing. Typing an up/down arrow key goes to the bottom/top line.
Ideally, showing a track should work the same way as hiding it, and keep the highlight.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-495)