avcodec/libutvideodec: use av_frame_move_ref()

AVFrames cannot be copied literally, their definition is in
avutil and their extended_data can point to their data[]
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/libutvideodec.cpp

@@ -164,7 +164,7 @@ static int utvideo_decode_frame(AVCodecContext *avctx, void *data,
     }
 
     *got_frame = 1;
-    *(AVFrame *)data = *pic;
+    av_frame_move_ref((AVFrame*)data, pic);
 
     return avpkt->size;
 }