If the DefaultAudioSink was reconfigured in a way that was compatible with the
previous configuration just after having been reset, we would try to drain audio
processors despite not having an AudioTrack. This could result in a
NullPointerException if speed adjustment was active.
Fix this behavior by only trying to drain audio processors if we actually have
an AudioTrack.
PiperOrigin-RevId: 235355466
caeaa9574e