libavfilter/vf_showinfo.c:104: error: Null Dereference
  pointer `desc` last assigned on line 102 could be null and is dereferenced at line 104, column 26.

libavfilter/vf_showinfo.c:98:1: start of procedure filter_frame()
 96. }
 97. 
 98. static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
     ^
 99. {
100.     AVFilterContext *ctx = inlink->dst;

libavfilter/vf_showinfo.c:100:5: 
 98. static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 99. {
100.     AVFilterContext *ctx = inlink->dst;
         ^
101.     ShowInfoContext *showinfo = ctx->priv;
102.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);

libavfilter/vf_showinfo.c:101:5: 
 99. {
100.     AVFilterContext *ctx = inlink->dst;
101.     ShowInfoContext *showinfo = ctx->priv;
         ^
102.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
103.     uint32_t plane_checksum[4] = {0}, checksum = 0;

libavfilter/vf_showinfo.c:102:5: 
100.     AVFilterContext *ctx = inlink->dst;
101.     ShowInfoContext *showinfo = ctx->priv;
102.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
         ^
103.     uint32_t plane_checksum[4] = {0}, checksum = 0;
104.     int i, plane, vsub = desc->log2_chroma_h;

libavutil/pixdesc.c:1866:1: start of procedure av_pix_fmt_desc_get()
  1864. }
  1865. 
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1868:9: Taking false branch
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1868:24: Taking true branch
  1866. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1869:9: 
  1867. {
  1868.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1869.         return NULL;
                ^
  1870.     return &av_pix_fmt_descriptors[pix_fmt];
  1871. }

libavutil/pixdesc.c:1871:1: return from a call to av_pix_fmt_desc_get
  1869.         return NULL;
  1870.     return &av_pix_fmt_descriptors[pix_fmt];
  1871. }
        ^
  1872. 
  1873. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavfilter/vf_showinfo.c:103:5: 
101.     ShowInfoContext *showinfo = ctx->priv;
102.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
103.     uint32_t plane_checksum[4] = {0}, checksum = 0;
         ^
104.     int i, plane, vsub = desc->log2_chroma_h;
105. 

libavfilter/vf_showinfo.c:104:5: 
102.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(inlink->format);
103.     uint32_t plane_checksum[4] = {0}, checksum = 0;
104.     int i, plane, vsub = desc->log2_chroma_h;
         ^
105. 
106.     for (plane = 0; frame->data[plane] && plane < 4; plane++) {
