lavfi/movie: free packet on decoder error

Prevents infinite loop, see Ticket2556
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/src_movie.c

@@ -514,6 +514,9 @@ static int movie_push_frame(AVFilterContext *ctx, unsigned out_id)
     if (ret < 0) {
         av_log(ctx, AV_LOG_WARNING, "Decode error: %s\n", av_err2str(ret));
         av_frame_free(&movie->frame);
+        av_free_packet(&movie->pkt0);
+        movie->pkt0.size = 0;
+        movie->pkt0.data = NULL;
         return 0;
     }
     if (!ret)