Count of tracks in standard playlists not updated after deleting files

[ghost]

Expected behavior

Counter of standard playlists are cleaned up after deleting files.

Actual behavior

After removing audio files standard playlists still show the previous number of tracks, including the deleted one. The counter is not updated and tracks are not removed from the audioplayer_playlist_tracks table.
The deleted tracks are not listed as they were deleted from the audioplayer_tracks table during the cleanup process at app start.

Steps to reproduce the behavior

1. Open Audio Player, create a playlist, and add tracks per drag and drop.
2. Open Files app and delete some tracks, included in the playlist.
3. Open Audio Player and check the playlist counter in the sidebar. Count the tracks listed in playlist in main window. The number of tracks is different.

Possible solution

Deleting of tracks in audioplayer_playlist_tracks table which are no longer contained in audioplayer_tracks.

Server configuration

Audio Player version: (see /settings/apps)
2.1.0-beta.2