libswscale/utils.c:781: error: Null Dereference
  pointer `desc` last assigned on line 780 could be null and is dereferenced at line 781, column 10.

libswscale/utils.c:778:1: start of procedure getSubSampleFactors()
776. #endif /* HAVE_MMXEXT_INLINE */
777. 
778. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
     ^
779. {
780.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);

libswscale/utils.c:780:5: 
778. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
779. {
780.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
         ^
781.     *h = desc->log2_chroma_w;
782.     *v = desc->log2_chroma_h;

libavutil/pixdesc.c:1468:1: start of procedure av_pix_fmt_desc_get()
  1466. }
  1467. 
  1468. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1469. {
  1470.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1470:9: Taking false branch
  1468. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1469. {
  1470.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1471.         return NULL;
  1472.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1470:24: Taking true branch
  1468. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1469. {
  1470.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1471.         return NULL;
  1472.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1471:9: 
  1469. {
  1470.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1471.         return NULL;
                ^
  1472.     return &av_pix_fmt_descriptors[pix_fmt];
  1473. }

libavutil/pixdesc.c:1473:1: return from a call to av_pix_fmt_desc_get
  1471.         return NULL;
  1472.     return &av_pix_fmt_descriptors[pix_fmt];
  1473. }
        ^
  1474. 
  1475. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/utils.c:781:5: 
779. {
780.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
781.     *h = desc->log2_chroma_w;
         ^
782.     *v = desc->log2_chroma_h;
783. }
