avconv.c:1638: error: Null Dereference
  pointer `desc` last assigned on line 1635 could be null and is dereferenced at line 1638, column 15.

avconv.c:1628:1: start of procedure get_format()
1626. }
1627. 
1628. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
      ^
1629. {
1630.     InputStream *ist = s->opaque;

avconv.c:1630:5: 
1628. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
1629. {
1630.     InputStream *ist = s->opaque;
          ^
1631.     const enum AVPixelFormat *p;
1632.     int ret;

avconv.c:1634:10: 
1632.     int ret;
1633. 
1634.     for (p = pix_fmts; *p != -1; p++) {
               ^
1635.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1636.         const HWAccel *hwaccel;

avconv.c:1634:24: Loop condition is true. Entering loop body
1632.     int ret;
1633. 
1634.     for (p = pix_fmts; *p != -1; p++) {
                             ^
1635.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1636.         const HWAccel *hwaccel;

avconv.c:1635:9: 
1633. 
1634.     for (p = pix_fmts; *p != -1; p++) {
1635.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
              ^
1636.         const HWAccel *hwaccel;
1637. 

libavutil/pixdesc.c:1893:1: start of procedure av_pix_fmt_desc_get()
  1891. }
  1892. 
  1893. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1894. {
  1895.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1895:9: Taking false branch
  1893. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1894. {
  1895.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1896.         return NULL;
  1897.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1895:24: Taking true branch
  1893. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1894. {
  1895.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1896.         return NULL;
  1897.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1896:9: 
  1894. {
  1895.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1896.         return NULL;
                ^
  1897.     return &av_pix_fmt_descriptors[pix_fmt];
  1898. }

libavutil/pixdesc.c:1898:1: return from a call to av_pix_fmt_desc_get
  1896.         return NULL;
  1897.     return &av_pix_fmt_descriptors[pix_fmt];
  1898. }
        ^
  1899. 
  1900. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

avconv.c:1638:15: 
1636.         const HWAccel *hwaccel;
1637. 
1638.         if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
                    ^
1639.             break;
1640. 
