MusicPlayer.playlist_index behaviour does not match documentation#2119

The documentation for MusicPlayer.playlist_index states that the value of playlist_index will be “-1 if no playlist audioclip is playing” which is not true.
playlist_index will be the index of whichever audioclip is selected in the current playlist regardless of the state of the currently playing audioclip.

Additionally, you can change the playlist_index without it having any effect on the behaviour of MusicPlayer.play().