libavfilter/vf_gradfun.c:171: error: Null Dereference
  pointer `desc` last assigned on line 170 could be null and is dereferenced at line 171, column 16.

libavfilter/vf_gradfun.c:167:1: start of procedure config_input()
165. }
166. 
167. static int config_input(AVFilterLink *inlink)
     ^
168. {
169.     GradFunContext *gf = inlink->dst->priv;

libavfilter/vf_gradfun.c:169:5: 
167. static int config_input(AVFilterLink *inlink)
168. {
169.     GradFunContext *gf = inlink->dst->priv;
         ^
170.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
171.     int hsub = desc->log2_chroma_w;

libavfilter/vf_gradfun.c:170:5: 
168. {
169.     GradFunContext *gf = inlink->dst->priv;
170.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
         ^
171.     int hsub = desc->log2_chroma_w;
172.     int vsub = desc->log2_chroma_h;

libavutil/pixdesc.c:1199:1: start of procedure av_pix_fmt_desc_get()
  1197. }
  1198. 
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1201:9: Taking false branch
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1201:24: Taking true branch
  1199. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1202:9: 
  1200. {
  1201.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1202.         return NULL;
                ^
  1203.     return &av_pix_fmt_descriptors[pix_fmt];
  1204. }

libavutil/pixdesc.c:1204:1: return from a call to av_pix_fmt_desc_get
  1202.         return NULL;
  1203.     return &av_pix_fmt_descriptors[pix_fmt];
  1204. }
        ^
  1205. 
  1206. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_gradfun.c:171:5: 
169.     GradFunContext *gf = inlink->dst->priv;
170.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
171.     int hsub = desc->log2_chroma_w;
         ^
172.     int vsub = desc->log2_chroma_h;
173. 
