avtools/avconv.c:1653: error: Null Dereference
  pointer `desc` last assigned on line 1650 could be null and is dereferenced at line 1653, column 15.

avtools/avconv.c:1643:1: start of procedure get_format()
1641. }
1642. 
1643. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
      ^
1644. {
1645.     InputStream *ist = s->opaque;

avtools/avconv.c:1645:5: 
1643. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
1644. {
1645.     InputStream *ist = s->opaque;
          ^
1646.     const enum AVPixelFormat *p;
1647.     int ret;

avtools/avconv.c:1649:10: 
1647.     int ret;
1648. 
1649.     for (p = pix_fmts; *p != -1; p++) {
               ^
1650.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1651.         const HWAccel *hwaccel;

avtools/avconv.c:1649:24: Loop condition is true. Entering loop body
1647.     int ret;
1648. 
1649.     for (p = pix_fmts; *p != -1; p++) {
                             ^
1650.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1651.         const HWAccel *hwaccel;

avtools/avconv.c:1650:9: 
1648. 
1649.     for (p = pix_fmts; *p != -1; p++) {
1650.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
              ^
1651.         const HWAccel *hwaccel;
1652. 

libavutil/pixdesc.c:1894:1: start of procedure av_pix_fmt_desc_get()
  1892. }
  1893. 
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1896:9: Taking false branch
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1896:24: Taking true branch
  1894. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1897:9: 
  1895. {
  1896.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1897.         return NULL;
                ^
  1898.     return &av_pix_fmt_descriptors[pix_fmt];
  1899. }

libavutil/pixdesc.c:1899:1: return from a call to av_pix_fmt_desc_get
  1897.         return NULL;
  1898.     return &av_pix_fmt_descriptors[pix_fmt];
  1899. }
        ^
  1900. 
  1901. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

avtools/avconv.c:1653:15: 
1651.         const HWAccel *hwaccel;
1652. 
1653.         if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
                    ^
1654.             break;
1655. 
