libavcodec/mpegvideo.c:1663: error: Null Dereference
  pointer `desc` last assigned on line 1662 could be null and is dereferenced at line 1663, column 22.

libavcodec/mpegvideo.c:1645:1: start of procedure ff_MPV_frame_end()
1643. 
1644. /* called after a frame has been decoded. */
1645. void ff_MPV_frame_end(MpegEncContext *s)
      ^
1646. {
1647. #if FF_API_XVMC

libavcodec/mpegvideo.c:1651:9: Taking false branch
1649.     /* redraw edges for the frame if decoding didn't complete */
1650.     // just to make sure that all data is rendered.
1651.     if (CONFIG_MPEG_XVMC_DECODER && s->avctx->xvmc_acceleration) {
              ^
1652.         ff_xvmc_field_end(s);
1653.     } else

libavcodec/mpegvideo.c:1656:9: Taking true branch
1654. FF_ENABLE_DEPRECATION_WARNINGS
1655. #endif /* FF_API_XVMC */
1656.     if (s->er.error_count  &&
              ^
1657.         !s->avctx->hwaccel &&
1658.         s->unrestricted_mv &&

libavcodec/mpegvideo.c:1657:10: Taking true branch
1655. #endif /* FF_API_XVMC */
1656.     if (s->er.error_count  &&
1657.         !s->avctx->hwaccel &&
               ^
1658.         s->unrestricted_mv &&
1659.         s->current_picture.reference &&

libavcodec/mpegvideo.c:1658:9: Taking true branch
1656.     if (s->er.error_count  &&
1657.         !s->avctx->hwaccel &&
1658.         s->unrestricted_mv &&
              ^
1659.         s->current_picture.reference &&
1660.         !s->intra_only &&

libavcodec/mpegvideo.c:1659:9: Taking true branch
1657.         !s->avctx->hwaccel &&
1658.         s->unrestricted_mv &&
1659.         s->current_picture.reference &&
              ^
1660.         !s->intra_only &&
1661.         !(s->flags & CODEC_FLAG_EMU_EDGE)) {

libavcodec/mpegvideo.c:1660:10: Taking true branch
1658.         s->unrestricted_mv &&
1659.         s->current_picture.reference &&
1660.         !s->intra_only &&
               ^
1661.         !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1662.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);

libavcodec/mpegvideo.c:1661:11: Taking true branch
1659.         s->current_picture.reference &&
1660.         !s->intra_only &&
1661.         !(s->flags & CODEC_FLAG_EMU_EDGE)) {
                ^
1662.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1663.         int hshift = desc->log2_chroma_w;

libavcodec/mpegvideo.c:1662:9: 
1660.         !s->intra_only &&
1661.         !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1662.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
              ^
1663.         int hshift = desc->log2_chroma_w;
1664.         int vshift = desc->log2_chroma_h;

libavutil/pixdesc.c:1507:1: start of procedure av_pix_fmt_desc_get()
  1505. }
  1506. 
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1509:9: Taking false branch
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1509:24: Taking true branch
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1510:9: 
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1510.         return NULL;
                ^
  1511.     return &av_pix_fmt_descriptors[pix_fmt];
  1512. }

libavutil/pixdesc.c:1512:1: return from a call to av_pix_fmt_desc_get
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];
  1512. }
        ^
  1513. 
  1514. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/mpegvideo.c:1663:9: 
1661.         !(s->flags & CODEC_FLAG_EMU_EDGE)) {
1662.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1663.         int hshift = desc->log2_chroma_w;
              ^
1664.         int vshift = desc->log2_chroma_h;
1665.         s->dsp.draw_edges(s->current_picture.f.data[0], s->linesize,
