avconv.c:1639: error: Null Dereference
  pointer `desc` last assigned on line 1636 could be null and is dereferenced at line 1639, column 15.

avconv.c:1629:1: start of procedure get_format()
1627. }
1628. 
1629. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
      ^
1630. {
1631.     InputStream *ist = s->opaque;

avconv.c:1631:5: 
1629. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
1630. {
1631.     InputStream *ist = s->opaque;
          ^
1632.     const enum AVPixelFormat *p;
1633.     int ret;

avconv.c:1635:10: 
1633.     int ret;
1634. 
1635.     for (p = pix_fmts; *p != -1; p++) {
               ^
1636.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1637.         const HWAccel *hwaccel;

avconv.c:1635:24: Loop condition is true. Entering loop body
1633.     int ret;
1634. 
1635.     for (p = pix_fmts; *p != -1; p++) {
                             ^
1636.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1637.         const HWAccel *hwaccel;

avconv.c:1636:9: 
1634. 
1635.     for (p = pix_fmts; *p != -1; p++) {
1636.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
              ^
1637.         const HWAccel *hwaccel;
1638. 

libavutil/pixdesc.c:1840:1: start of procedure av_pix_fmt_desc_get()
  1838. }
  1839. 
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1842:9: Taking false branch
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1842:24: Taking true branch
  1840. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1843:9: 
  1841. {
  1842.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1843.         return NULL;
                ^
  1844.     return &av_pix_fmt_descriptors[pix_fmt];
  1845. }

libavutil/pixdesc.c:1845:1: return from a call to av_pix_fmt_desc_get
  1843.         return NULL;
  1844.     return &av_pix_fmt_descriptors[pix_fmt];
  1845. }
        ^
  1846. 
  1847. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

avconv.c:1639:15: 
1637.         const HWAccel *hwaccel;
1638. 
1639.         if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
                    ^
1640.             break;
1641. 
