With audiodev parameter out.mixing-engine=off hw->mix_buf is
NULL. This patch reverts a small part of dc88e38fa7 "audio:
unify input and output mixeng buffer management".

To reproduce the problem start qemu with
-audiodev oss,id=audio0,try-mmap=on,out.mixing-engine=off

Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
---
 audio/ossaudio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/audio/ossaudio.c b/audio/ossaudio.c
index 4965084a5a..6a3b78b381 100644
--- a/audio/ossaudio.c
+++ b/audio/ossaudio.c
@@ -592,7 +592,7 @@ static void oss_enable_out(HWVoiceOut *hw, bool enable)
             return;
         }
 
-        audio_pcm_info_clear_buf(&hw->info, hw->buf_emul, hw->mix_buf->size);
+        audio_pcm_info_clear_buf(&hw->info, hw->buf_emul, hw->samples);
         trig = PCM_ENABLE_OUTPUT;
         if (ioctl(oss->fd, SNDCTL_DSP_SETTRIGGER, &trig) < 0) {
             oss_logerr(errno,
-- 
2.16.4