libswscale/utils.c:800: error: Null Dereference
  pointer `desc` last assigned on line 799 could be null and is dereferenced at line 800, column 10.

libswscale/utils.c:797:1: start of procedure getSubSampleFactors()
795. #endif /* HAVE_MMXEXT_INLINE */
796. 
797. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
     ^
798. {
799.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);

libswscale/utils.c:799:5: 
797. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
798. {
799.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
         ^
800.     *h = desc->log2_chroma_w;
801.     *v = desc->log2_chroma_h;

libavutil/pixdesc.c:1894:1: start of procedure av_pix_fmt_desc_get()
  1892. }
  1893. 
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1896:9: Taking false branch
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1896:24: Taking true branch
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1897:9: 
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1897.         return NULL;
                ^
  1898.     return &av_pix_fmt_descriptors[pix_fmt];
  1899. }

libavutil/pixdesc.c:1899:1: return from a call to av_pix_fmt_desc_get
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];
  1899. }
        ^
  1900. 
  1901. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/utils.c:800:5: 
798. {
799.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
800.     *h = desc->log2_chroma_w;
         ^
801.     *v = desc->log2_chroma_h;
802. }
