Fix section hiding

We were suppressing hiding when section contained previous track.

Now, when all are played, we hide.

app/playlistmodel.py

@@ -124,7 +124,6 @@ class PlaylistModel(QAbstractTableModel):
             for ts in [
                 track_sequence.next,
                 track_sequence.current,
-                track_sequence.previous,
             ]:
                 if ts and ts.row_number == row_number and ts.playlist_id == self.playlist_id:
                     break