avcodec/mss3: Remove unnecessary free of unallocated frame

The frame will only be allocated a few lines below.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/mss3.c

@@ -844,7 +844,6 @@ static av_cold int mss3_decode_init(AVCodecContext *avctx)
                                             b_width * b_height);
         if (!c->dct_coder[i].prev_dc) {
             av_log(avctx, AV_LOG_ERROR, "Cannot allocate buffer\n");
-            av_frame_free(&c->pic);
             while (i >= 0) {
                 av_freep(&c->dct_coder[i].prev_dc);
                 i--;