libavfilter/vf_scale.c:270: error: Null Dereference
  pointer `desc` last assigned on line 265 could be null and is dereferenced at line 270, column 19.

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

libavfilter/vf_scale.c:262:5: 
260. static int filter_frame(AVFilterLink *link, AVFrame *in)
261. {
262.     ScaleContext *scale = link->dst->priv;
         ^
263.     AVFilterLink *outlink = link->dst->outputs[0];
264.     AVFrame *out;

libavfilter/vf_scale.c:263:5: 
261. {
262.     ScaleContext *scale = link->dst->priv;
263.     AVFilterLink *outlink = link->dst->outputs[0];
         ^
264.     AVFrame *out;
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.     AVFrame *out;
265.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
         ^
266. 
267.     if (!scale->sws)

libavutil/pixdesc.c:1440:1: start of procedure av_pix_fmt_desc_get()
  1438. }
  1439. 
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1442:9: Taking false branch
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1442:24: Taking true branch
  1440. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1443:9: 
  1441. {
  1442.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1443.         return NULL;
                ^
  1444.     return &av_pix_fmt_descriptors[pix_fmt];
  1445. }

libavutil/pixdesc.c:1445:1: return from a call to av_pix_fmt_desc_get
  1443.         return NULL;
  1444.     return &av_pix_fmt_descriptors[pix_fmt];
  1445. }
        ^
  1446. 
  1447. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_scale.c:267:10: Taking false branch
265.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
266. 
267.     if (!scale->sws)
              ^
268.         return ff_filter_frame(outlink, in);
269. 

libavfilter/vf_scale.c:270:5: 
268.         return ff_filter_frame(outlink, in);
269. 
270.     scale->hsub = desc->log2_chroma_w;
         ^
271.     scale->vsub = desc->log2_chroma_h;
272. 
