libavfilter/vf_scale.c:275: error: Null Dereference
  pointer `desc` last assigned on line 265 could be null and is dereferenced at line 275, column 19.

libavfilter/vf_scale.c:260:1: start of procedure start_frame()
258. }
259. 
260. static int start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
     ^
261. {
262.     ScaleContext *scale = link->dst->priv;

libavfilter/vf_scale.c:262:5: 
260. static int start_frame(AVFilterLink *link, AVFilterBufferRef *picref)
261. {
262.     ScaleContext *scale = link->dst->priv;
         ^
263.     AVFilterLink *outlink = link->dst->outputs[0];
264.     AVFilterBufferRef *outpicref, *for_next_filter;

libavfilter/vf_scale.c:263:5: 
261. {
262.     ScaleContext *scale = link->dst->priv;
263.     AVFilterLink *outlink = link->dst->outputs[0];
         ^
264.     AVFilterBufferRef *outpicref, *for_next_filter;
265.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);

libavfilter/vf_scale.c:265:5: 
263.     AVFilterLink *outlink = link->dst->outputs[0];
264.     AVFilterBufferRef *outpicref, *for_next_filter;
265.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
         ^
266.     int ret = 0;
267. 

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_scale.c:266:5: 
264.     AVFilterBufferRef *outpicref, *for_next_filter;
265.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
266.     int ret = 0;
         ^
267. 
268.     if (!scale->sws) {

libavfilter/vf_scale.c:268:10: Taking false branch
266.     int ret = 0;
267. 
268.     if (!scale->sws) {
              ^
269.         outpicref = avfilter_ref_buffer(picref, ~0);
270.         if (!outpicref)

libavfilter/vf_scale.c:275:5: 
273.     }
274. 
275.     scale->hsub = desc->log2_chroma_w;
         ^
276.     scale->vsub = desc->log2_chroma_h;
277. 
