In `WPPlaylistView::ended()`, at the end of a playlist, set the index to `0` and call `->setCurrent()` instead of `->loadCurrent()` so that the first track is properly highlighted.

Fixes #28428.

Built from https://develop.svn.wordpress.org/trunk@28649


git-svn-id: http://core.svn.wordpress.org/trunk@28467 1a063a9b-81f0-0310-95a4-ce76da25c4cd