getting this.shifter is null

[webciter]

trying to play cdg zip file with mp3 and getting this.shifter and stuck on the first frame

triggered here
}, { key: "start", value: function() { var t = this; X.call(this, this.ctx, this.canvas), this.shifter.connect(this.gainNode), this.gainNode.connect(this.audio.destination), this.audio.resume().then((function() { t.props.isPlaying = !0, t.player.play() })) } }, {