function bindSongEnded() {
    _config2.default.audio.removeEventListener("ended", _ended2.default.handle);
    _config2.default.audio.addEventListener("ended", _ended2.default.handle);
  }
When the audio element has ended playing, we handle the song
ending. In a single song or multiple modular song instance,
this just synchronizes the visuals for time and song time
visualization, but for a playlist it determines whether
it should play the next song or not.

@access private