NPE when attempting to exit Dash streaming

[oseparovic]

Doesn't happen every time. Might be caused by leaving VideoViewActivity at some point during the initialization before it has fully completed.

Oneplus 3 - A300
Android 8.0.0

I/MediaCodec: stop
D/SurfaceUtils: disconnecting from surface 0x75a45ff010, reason disconnectFromSurface
06-11 15:49:59.509 1202-1375/? I/OMX-VDEC-1080P: omx_vdec::component_deinit() complete
06-11 15:49:59.513 1202-1375/? I/OMX-VDEC-1080P: Exit OMX vdec Destructor: fd=13
    Video slvp perflock released
D/MediaCodecVideoDecoder: decoder released
I/MediaCodec: stop
D/MediaCodecAudioDecoder: decoder released
I/android.media.AudioTrack: stop() packageName: : 44100
D/AudioTrack: stop() called with 105472 frames delivered
I/android.media.AudioTrack: stop() packageName: : 44100
E/AndroidRuntime: FATAL EXCEPTION: AudioPlayback
    Process: , PID: 9918
    java.lang.NullPointerException: Attempt to invoke virtual method 'int android.media.AudioTrack.write(byte[], int, int)' on a null object reference
        at net.protyposis.android.mediaplayer.AudioPlayback.writeToPlaybackBuffer(AudioPlayback.java:378)
        at net.protyposis.android.mediaplayer.AudioPlayback.access$300(AudioPlayback.java:36)
        at net.protyposis.android.mediaplayer.AudioPlayback$AudioThread.run(AudioPlayback.java:459)