libavcodec/h264dec.c:91: error: Null Dereference
  pointer `desc` last assigned on line 90 could be null and is dereferenced at line 91, column 18.

libavcodec/h264dec.c:85:1: start of procedure ff_h264_draw_horiz_band()
83. }
84. 
85. void ff_h264_draw_horiz_band(const H264Context *h, H264SliceContext *sl,
    ^
86.                              int y, int height)
87. {

libavcodec/h264dec.c:88:5: 
86.                              int y, int height)
87. {
88.     AVCodecContext *avctx = h->avctx;
        ^
89.     const AVFrame   *src  = h->cur_pic.f;
90.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);

libavcodec/h264dec.c:89:5: 
87. {
88.     AVCodecContext *avctx = h->avctx;
89.     const AVFrame   *src  = h->cur_pic.f;
        ^
90.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
91.     int vshift = desc->log2_chroma_h;

libavcodec/h264dec.c:90:5: 
88.     AVCodecContext *avctx = h->avctx;
89.     const AVFrame   *src  = h->cur_pic.f;
90.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
        ^
91.     int vshift = desc->log2_chroma_h;
92.     const int field_pic = h->picture_structure != PICT_FRAME;

libavutil/pixdesc.c:1740:1: start of procedure av_pix_fmt_desc_get()
  1738. }
  1739. 
  1740. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1741. {
  1742.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1742:9: Taking false branch
  1740. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1741. {
  1742.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1743.         return NULL;
  1744.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1742:24: Taking true branch
  1740. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1741. {
  1742.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1743.         return NULL;
  1744.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1743:9: 
  1741. {
  1742.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1743.         return NULL;
                ^
  1744.     return &av_pix_fmt_descriptors[pix_fmt];
  1745. }

libavutil/pixdesc.c:1745:1: return from a call to av_pix_fmt_desc_get
  1743.         return NULL;
  1744.     return &av_pix_fmt_descriptors[pix_fmt];
  1745. }
        ^
  1746. 
  1747. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/h264dec.c:91:5: 
89.     const AVFrame   *src  = h->cur_pic.f;
90.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
91.     int vshift = desc->log2_chroma_h;
        ^
92.     const int field_pic = h->picture_structure != PICT_FRAME;
93.     if (field_pic) {
