libavfilter/vf_gradfun.c:167: error: Null Dereference
  pointer `desc` last assigned on line 166 could be null and is dereferenced at line 167, column 16.

libavfilter/vf_gradfun.c:163:1: start of procedure config_input()
161. }
162. 
163. static int config_input(AVFilterLink *inlink)
     ^
164. {
165.     GradFunContext *s = inlink->dst->priv;

libavfilter/vf_gradfun.c:165:5: 
163. static int config_input(AVFilterLink *inlink)
164. {
165.     GradFunContext *s = inlink->dst->priv;
         ^
166.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
167.     int hsub = desc->log2_chroma_w;

libavfilter/vf_gradfun.c:166:5: 
164. {
165.     GradFunContext *s = inlink->dst->priv;
166.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
         ^
167.     int hsub = desc->log2_chroma_w;
168.     int vsub = desc->log2_chroma_h;

libavutil/pixdesc.c:1507:1: start of procedure av_pix_fmt_desc_get()
  1505. }
  1506. 
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1509:9: Taking false branch
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1509:24: Taking true branch
  1507. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1510:9: 
  1508. {
  1509.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1510.         return NULL;
                ^
  1511.     return &av_pix_fmt_descriptors[pix_fmt];
  1512. }

libavutil/pixdesc.c:1512:1: return from a call to av_pix_fmt_desc_get
  1510.         return NULL;
  1511.     return &av_pix_fmt_descriptors[pix_fmt];
  1512. }
        ^
  1513. 
  1514. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_gradfun.c:167:5: 
165.     GradFunContext *s = inlink->dst->priv;
166.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
167.     int hsub = desc->log2_chroma_w;
         ^
168.     int vsub = desc->log2_chroma_h;
169. 
