libavfilter/vf_scale.c:266: error: Null Dereference
  pointer `desc` last assigned on line 261 could be null and is dereferenced at line 266, column 19.

libavfilter/vf_scale.c:256:1: start of procedure filter_frame()
254. }
255. 
256. static int filter_frame(AVFilterLink *link, AVFrame *in)
     ^
257. {
258.     ScaleContext *scale = link->dst->priv;

libavfilter/vf_scale.c:258:5: 
256. static int filter_frame(AVFilterLink *link, AVFrame *in)
257. {
258.     ScaleContext *scale = link->dst->priv;
         ^
259.     AVFilterLink *outlink = link->dst->outputs[0];
260.     AVFrame *out;

libavfilter/vf_scale.c:259:5: 
257. {
258.     ScaleContext *scale = link->dst->priv;
259.     AVFilterLink *outlink = link->dst->outputs[0];
         ^
260.     AVFrame *out;
261.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);

libavfilter/vf_scale.c:261:5: 
259.     AVFilterLink *outlink = link->dst->outputs[0];
260.     AVFrame *out;
261.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
         ^
262. 
263.     if (!scale->sws)

libavutil/pixdesc.c:1504:1: start of procedure av_pix_fmt_desc_get()
  1502. }
  1503. 
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1506:9: Taking false branch
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1506:24: Taking true branch
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1507:9: 
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1507.         return NULL;
                ^
  1508.     return &av_pix_fmt_descriptors[pix_fmt];
  1509. }

libavutil/pixdesc.c:1509:1: return from a call to av_pix_fmt_desc_get
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];
  1509. }
        ^
  1510. 
  1511. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_scale.c:263:10: Taking false branch
261.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
262. 
263.     if (!scale->sws)
              ^
264.         return ff_filter_frame(outlink, in);
265. 

libavfilter/vf_scale.c:266:5: 
264.         return ff_filter_frame(outlink, in);
265. 
266.     scale->hsub = desc->log2_chroma_w;
         ^
267.     scale->vsub = desc->log2_chroma_h;
268. 
