libavcodec/mpegvideo_enc.c:1491: error: Null Dereference
  pointer `desc` last assigned on line 1490 could be null and is dereferenced at line 1491, column 22.

libavcodec/mpegvideo_enc.c:1483:1: start of procedure frame_end()
1481. }
1482. 
1483. static void frame_end(MpegEncContext *s)
      ^
1484. {
1485.     int i;

libavcodec/mpegvideo_enc.c:1487:9: Taking true branch
1485.     int i;
1486. 
1487.     if (s->unrestricted_mv &&
              ^
1488.         s->current_picture.reference &&
1489.         !s->intra_only) {

libavcodec/mpegvideo_enc.c:1488:9: Taking true branch
1486. 
1487.     if (s->unrestricted_mv &&
1488.         s->current_picture.reference &&
              ^
1489.         !s->intra_only) {
1490.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);

libavcodec/mpegvideo_enc.c:1489:10: Taking true branch
1487.     if (s->unrestricted_mv &&
1488.         s->current_picture.reference &&
1489.         !s->intra_only) {
               ^
1490.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1491.         int hshift = desc->log2_chroma_w;

libavcodec/mpegvideo_enc.c:1490:9: 
1488.         s->current_picture.reference &&
1489.         !s->intra_only) {
1490.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
              ^
1491.         int hshift = desc->log2_chroma_w;
1492.         int vshift = desc->log2_chroma_h;

libavutil/pixdesc.c:1866:1: start of procedure av_pix_fmt_desc_get()
  1864. }
  1865. 
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1868:9: Taking false branch
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1868:24: Taking true branch
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1869:9: 
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1869.         return NULL;
                ^
  1870.     return &av_pix_fmt_descriptors[pix_fmt];
  1871. }

libavutil/pixdesc.c:1871:1: return from a call to av_pix_fmt_desc_get
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];
  1871. }
        ^
  1872. 
  1873. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/mpegvideo_enc.c:1491:9: 
1489.         !s->intra_only) {
1490.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(s->avctx->pix_fmt);
1491.         int hshift = desc->log2_chroma_w;
              ^
1492.         int vshift = desc->log2_chroma_h;
1493.         s->mpvencdsp.draw_edges(s->current_picture.f->data[0], s->linesize,
