libswscale/utils.c:791: error: Null Dereference
  pointer `desc` last assigned on line 790 could be null and is dereferenced at line 791, column 10.

libswscale/utils.c:788:1: start of procedure getSubSampleFactors()
786. #endif /* HAVE_MMXEXT_INLINE */
787. 
788. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
     ^
789. {
790.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);

libswscale/utils.c:790:5: 
788. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
789. {
790.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
         ^
791.     *h = desc->log2_chroma_w;
792.     *v = desc->log2_chroma_h;

libavutil/pixdesc.c:1665:1: start of procedure av_pix_fmt_desc_get()
  1663. }
  1664. 
  1665. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1666. {
  1667.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1667:9: Taking false branch
  1665. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1666. {
  1667.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1668.         return NULL;
  1669.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1667:24: Taking true branch
  1665. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1666. {
  1667.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1668.         return NULL;
  1669.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1668:9: 
  1666. {
  1667.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1668.         return NULL;
                ^
  1669.     return &av_pix_fmt_descriptors[pix_fmt];
  1670. }

libavutil/pixdesc.c:1670:1: return from a call to av_pix_fmt_desc_get
  1668.         return NULL;
  1669.     return &av_pix_fmt_descriptors[pix_fmt];
  1670. }
        ^
  1671. 
  1672. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/utils.c:791:5: 
789. {
790.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
791.     *h = desc->log2_chroma_w;
         ^
792.     *v = desc->log2_chroma_h;
793. }
