libavcodec/mpegvideo.c:1742: error: Null Dereference
  pointer `desc` last assigned on line 1741 could be null and is dereferenced at line 1742, column 21.

libavcodec/mpegvideo.c:1727:1: start of procedure ff_MPV_frame_end()
1725. /* generic function for encode/decode called after a
1726.  * frame has been coded/decoded. */
1727. void ff_MPV_frame_end(MpegEncContext *s)
      ^
1728. {
1729.     int i;

libavcodec/mpegvideo.c:1732:9: Taking false branch
1730.     /* redraw edges for the frame if decoding didn't complete */
1731.     // just to make sure that all data is rendered.
1732.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
              ^
1733.         ff_xvmc_field_end(s);
1734.    } else if ((s->er.error_count || s->encoding) &&

libavcodec/mpegvideo.c:1734:16: Taking false branch
1732.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
1733.         ff_xvmc_field_end(s);
1734.    } else if ((s->er.error_count || s->encoding) &&
                     ^
1735.               !s->avctx->hwaccel &&
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&

libavcodec/mpegvideo.c:1734:37: Taking true branch
1732.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
1733.         ff_xvmc_field_end(s);
1734.    } else if ((s->er.error_count || s->encoding) &&
                                          ^
1735.               !s->avctx->hwaccel &&
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&

libavcodec/mpegvideo.c:1735:16: Taking true branch
1733.         ff_xvmc_field_end(s);
1734.    } else if ((s->er.error_count || s->encoding) &&
1735.               !s->avctx->hwaccel &&
                     ^
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1737.               s->unrestricted_mv &&

libavcodec/mpegvideo.c:1736:17: Taking true branch
1734.    } else if ((s->er.error_count || s->encoding) &&
1735.               !s->avctx->hwaccel &&
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
                      ^
1737.               s->unrestricted_mv &&
1738.               s->current_picture.reference &&

libavcodec/mpegvideo.c:1737:15: Taking true branch
1735.               !s->avctx->hwaccel &&
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1737.               s->unrestricted_mv &&
                    ^
1738.               s->current_picture.reference &&
1739.               !s->intra_only &&

libavcodec/mpegvideo.c:1738:15: Taking true branch
1736.               !(s->avctx->codec->capabilities & CODEC_CAP_HWACCEL_VDPAU) &&
1737.               s->unrestricted_mv &&
1738.               s->current_picture.reference &&
                    ^
1739.               !s->intra_only &&
1740.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {

libavcodec/mpegvideo.c:1739:16: Taking true branch
1737.               s->unrestricted_mv &&
1738.               s->current_picture.reference &&
1739.               !s->intra_only &&
                     ^
1740.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1741.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);

libavcodec/mpegvideo.c:1740:17: Taking true branch
1738.               s->current_picture.reference &&
1739.               !s->intra_only &&
1740.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
                      ^
1741.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1742.        int hshift = desc->log2_chroma_w;

libavcodec/mpegvideo.c:1741:8: 
1739.               !s->intra_only &&
1740.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1741.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
             ^
1742.        int hshift = desc->log2_chroma_w;
1743.        int vshift = desc->log2_chroma_h;

libavutil/pixdesc.c:1440:1: start of procedure av_pix_fmt_desc_get()
  1438. }
  1439. 
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1442:9: Taking false branch
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1442:24: Taking true branch
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1443:9: 
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1443.         return NULL;
                ^
  1444.     return &av_pix_fmt_descriptors[pix_fmt];
  1445. }

libavutil/pixdesc.c:1445:1: return from a call to av_pix_fmt_desc_get
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];
  1445. }
        ^
  1446. 
  1447. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/mpegvideo.c:1742:8: 
1740.               !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1741.        const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1742.        int hshift = desc->log2_chroma_w;
             ^
1743.        int vshift = desc->log2_chroma_h;
1744.        s->dsp.draw_edges(s->current_picture.f.data[0], s->linesize,
