libswscale/utils.c:792: error: Null Dereference
  pointer `desc` last assigned on line 791 could be null and is dereferenced at line 792, column 10.

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

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

libavutil/pixdesc.c:1840:1: start of procedure av_pix_fmt_desc_get()
  1838. }
  1839. 
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1842:9: Taking false branch
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1842:24: Taking true branch
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1843:9: 
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1843.         return NULL;
                ^
  1844.     return &av_pix_fmt_descriptors[pix_fmt];
  1845. }

libavutil/pixdesc.c:1845:1: return from a call to av_pix_fmt_desc_get
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];
  1845. }
        ^
  1846. 
  1847. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/utils.c:792:5: 
790. {
791.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
792.     *h = desc->log2_chroma_w;
         ^
793.     *v = desc->log2_chroma_h;
794. }
