blockingClearSurface cause IllegalStateException

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Hi, I've just noticed that some methods in the wrapper seems not working.
Steps:
1) I've playing player, all is okay
2)I've called the method
public void blockingClearSurface() {
surface = null;
pushSurfaceAndVideoTrack(true);
}
from ExoPlayerWrapper.
3) I've called setSurface(..) with legal Surface, but demo app crashes with log like:

09-28 20:19:37.774 511-960/com.conax.golive.access.defaultOperator E/ExoPlayerImplInternal﹕ Internal runtime error.
java.lang.IllegalStateException: buffer was freed
at java.nio.DirectByteBuffer.checkNotFreed(DirectByteBuffer.java:557)
at java.nio.DirectByteBuffer.checkIsAccessible(DirectByteBuffer.java:549)
at java.nio.DirectByteBuffer.put(DirectByteBuffer.java:352)
at com.conax.util.binary.bytes.data.custom.PreallocatedBufferBytesData.writeToByteBuffer(PreallocatedBufferBytesData.java:155)
at com.conax.util.binary.bytes.Bytes.writeToByteBuffer(Bytes.java:495)
at com.google.android.exoplayer.conaxhls.HLSTrack.readOneSample(HLSTrack.java:138)
at com.google.android.exoplayer.conaxhls.HLSTrack.readSample(HLSTrack.java:115)
at com.google.android.exoplayer.conaxhls.HLSSampleSource.readData(HLSSampleSource.java:332)
at com.google.android.exoplayer.MediaCodecTrackRenderer.readFormat(MediaCodecTrackRenderer.java:523)
at com.google.android.exoplayer.MediaCodecTrackRenderer.doSomeWork(MediaCodecTrackRenderer.java:505)
at com.google.android.exoplayer.ExoPlayerImplInternal.doSomeWork(ExoPlayerImplInternal.java:400)
at com.google.android.exoplayer.ExoPlayerImplInternal.handleMessage(ExoPlayerImplInternal.java:203)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:135)
at android.os.HandlerThread.run(HandlerThread.java:61)
at com.google.android.exoplayer.util.PriorityHandlerThread.run(PriorityHandlerThread.java:40)
09-28 20:19:37.799 511-511/com.conax.golive.access.defaultOperator E/com.conax.client.ottaccess.exo.ExoPlayerWrapper﹕ onPlayerError: java.lang.IllegalStateException: buffer was freed

Start with ExoPlayerWrapper.blockingClearSurface() and trace pushSurfaceAndVideoTrack(true), then reproduce the sequence of clearing and resetting the Surface. Use the supplied IllegalStateException stack trace to follow the failure through ExoPlayerImplInternal and HLSTrack; done means the sequence no longer produces the reported buffer error.

Written by the indexing model from the issue text.