libavfilter/vf_scale.c:263: error: Null Dereference
  pointer `desc` last assigned on line 258 could be null and is dereferenced at line 263, column 19.

libavfilter/vf_scale.c:253:1: start of procedure filter_frame()
251. }
252. 
253. static int filter_frame(AVFilterLink *link, AVFrame *in)
     ^
254. {
255.     ScaleContext *scale = link->dst->priv;

libavfilter/vf_scale.c:255:5: 
253. static int filter_frame(AVFilterLink *link, AVFrame *in)
254. {
255.     ScaleContext *scale = link->dst->priv;
         ^
256.     AVFilterLink *outlink = link->dst->outputs[0];
257.     AVFrame *out;

libavfilter/vf_scale.c:256:5: 
254. {
255.     ScaleContext *scale = link->dst->priv;
256.     AVFilterLink *outlink = link->dst->outputs[0];
         ^
257.     AVFrame *out;
258.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);

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

libavutil/pixdesc.c:1464:1: start of procedure av_pix_fmt_desc_get()
  1462. }
  1463. 
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1466:9: Taking false branch
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1466:24: Taking true branch
  1464. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1467:9: 
  1465. {
  1466.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1467.         return NULL;
                ^
  1468.     return &av_pix_fmt_descriptors[pix_fmt];
  1469. }

libavutil/pixdesc.c:1469:1: return from a call to av_pix_fmt_desc_get
  1467.         return NULL;
  1468.     return &av_pix_fmt_descriptors[pix_fmt];
  1469. }
        ^
  1470. 
  1471. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_scale.c:260:10: Taking false branch
258.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(link->format);
259. 
260.     if (!scale->sws)
              ^
261.         return ff_filter_frame(outlink, in);
262. 

libavfilter/vf_scale.c:263:5: 
261.         return ff_filter_frame(outlink, in);
262. 
263.     scale->hsub = desc->log2_chroma_w;
         ^
264.     scale->vsub = desc->log2_chroma_h;
265. 
