libswscale/swscale_unscaled.c:1200: error: Null Dereference
  pointer `desc` last assigned on line 1196 could be null and is dereferenced at line 1200, column 21.

libswscale/swscale_unscaled.c:1193:1: start of procedure check_image_pointers()
1191. }
1192. 
1193. static int check_image_pointers(uint8_t *data[4], enum AVPixelFormat pix_fmt,
      ^
1194.                                 const int linesizes[4])
1195. {

libswscale/swscale_unscaled.c:1196:5: 
1194.                                 const int linesizes[4])
1195. {
1196.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(pix_fmt);
          ^
1197.     int i;
1198. 

libavutil/pixdesc.c:1914:1: start of procedure av_pix_fmt_desc_get()
  1912. }
  1913. 
  1914. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1915. {
  1916.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1916:9: Taking false branch
  1914. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1915. {
  1916.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1917.         return NULL;
  1918.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1916:24: Taking true branch
  1914. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1915. {
  1916.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1917.         return NULL;
  1918.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1917:9: 
  1915. {
  1916.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1917.         return NULL;
                ^
  1918.     return &av_pix_fmt_descriptors[pix_fmt];
  1919. }

libavutil/pixdesc.c:1919:1: return from a call to av_pix_fmt_desc_get
  1917.         return NULL;
  1918.     return &av_pix_fmt_descriptors[pix_fmt];
  1919. }
        ^
  1920. 
  1921. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libswscale/swscale_unscaled.c:1199:10: 
1197.     int i;
1198. 
1199.     for (i = 0; i < 4; i++) {
               ^
1200.         int plane = desc->comp[i].plane;
1201.         if (!data[plane] || !linesizes[plane])

libswscale/swscale_unscaled.c:1199:17: Loop condition is true. Entering loop body
1197.     int i;
1198. 
1199.     for (i = 0; i < 4; i++) {
                      ^
1200.         int plane = desc->comp[i].plane;
1201.         if (!data[plane] || !linesizes[plane])

libswscale/swscale_unscaled.c:1200:9: 
1198. 
1199.     for (i = 0; i < 4; i++) {
1200.         int plane = desc->comp[i].plane;
              ^
1201.         if (!data[plane] || !linesizes[plane])
1202.             return 0;
