libavfilter/vf_drawbox.c:86: error: Null Dereference
  pointer `desc` last assigned on line 84 could be null and is dereferenced at line 86, column 21.

libavfilter/vf_drawbox.c:81:1: start of procedure config_input()
79. }
80. 
81. static int config_input(AVFilterLink *inlink)
    ^
82. {
83.     DrawBoxContext *drawbox = inlink->dst->priv;

libavfilter/vf_drawbox.c:83:5: 
81. static int config_input(AVFilterLink *inlink)
82. {
83.     DrawBoxContext *drawbox = inlink->dst->priv;
        ^
84.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
85. 

libavfilter/vf_drawbox.c:84:5: 
82. {
83.     DrawBoxContext *drawbox = inlink->dst->priv;
84.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
        ^
85. 
86.     drawbox->hsub = desc->log2_chroma_w;

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_drawbox.c:86:5: 
84.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
85. 
86.     drawbox->hsub = desc->log2_chroma_w;
        ^
87.     drawbox->vsub = desc->log2_chroma_h;
88. 
