Merge commit 'a2816230'

* commit 'a2816230':
  avframe: call release_buffer only if it is set

Conflicts:
	libavcodec/utils.c
Merged-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/utils.c

@@ -669,7 +669,8 @@ typedef struct CompatReleaseBufPriv {
 static void compat_free_buffer(void *opaque, uint8_t *data)
 {
     CompatReleaseBufPriv *priv = opaque;
-    priv->avctx.release_buffer(&priv->avctx, &priv->frame);
+    if (priv->avctx.release_buffer)
+        priv->avctx.release_buffer(&priv->avctx, &priv->frame);
     av_freep(&priv);
 }