libswscale/utils.c:771: error: Null Dereference
  pointer `desc` last assigned on line 770 could be null and is dereferenced at line 771, column 10.

libswscale/utils.c:768:1: start of procedure getSubSampleFactors()
766. #endif /* HAVE_MMXEXT_INLINE */
767. 
768. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
     ^
769. {
770.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);

libswscale/utils.c:770:5: 
768. static void getSubSampleFactors(int *h, int *v, enum AVPixelFormat format)
769. {
770.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
         ^
771.     *h = desc->log2_chroma_w;
772.     *v = desc->log2_chroma_h;

libavutil/pixdesc.c:1433:1: start of procedure av_pix_fmt_desc_get()
  1431. }
  1432. 
  1433. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1434. {
  1435.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1435:9: Taking false branch
  1433. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1434. {
  1435.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1436.         return NULL;
  1437.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1435:24: Taking true branch
  1433. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1434. {
  1435.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1436.         return NULL;
  1437.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1436:9: 
  1434. {
  1435.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1436.         return NULL;
                ^
  1437.     return &av_pix_fmt_descriptors[pix_fmt];
  1438. }

libavutil/pixdesc.c:1438:1: return from a call to av_pix_fmt_desc_get
  1436.         return NULL;
  1437.     return &av_pix_fmt_descriptors[pix_fmt];
  1438. }
        ^
  1439. 
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/utils.c:771:5: 
769. {
770.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(format);
771.     *h = desc->log2_chroma_w;
         ^
772.     *v = desc->log2_chroma_h;
773. }
