xmvdemux: prefer av_freep() to deallocate audio stream structs.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/xmv.c

@@ -546,7 +546,7 @@ static int xmv_read_close(AVFormatContext *s)
 {
     XMVDemuxContext *xmv = s->priv_data;
 
-    av_free(xmv->audio);
+    av_freep(&xmv->audio);
 
     return 0;
 }