avcodec/a64multienc: use av_frame_ref instead of copying the frame

This fixes freeing the frame buffer twice on cleanup leading to a crash.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 39e4ed7c1d)

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

libavcodec/a64multienc.c

@@ -317,7 +317,9 @@ static int a64multi_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     } else {
         /* fill up mc_meta_charset with data until lifetime exceeds */
         if (c->mc_frame_counter < c->mc_lifetime) {
-            *p = *pict;
+            ret = av_frame_ref(p, pict);
+            if (ret < 0)
+                return ret;
             p->pict_type = AV_PICTURE_TYPE_I;
             p->key_frame = 1;
             to_meta_with_crop(avctx, p, meta + 32000 * c->mc_frame_counter);