avtools/avconv.c:1647: error: Null Dereference
  pointer `desc` last assigned on line 1644 could be null and is dereferenced at line 1647, column 15.

avtools/avconv.c:1637:1: start of procedure get_format()
1635. }
1636. 
1637. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
      ^
1638. {
1639.     InputStream *ist = s->opaque;

avtools/avconv.c:1639:5: 
1637. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
1638. {
1639.     InputStream *ist = s->opaque;
          ^
1640.     const enum AVPixelFormat *p;
1641.     int ret;

avtools/avconv.c:1643:10: 
1641.     int ret;
1642. 
1643.     for (p = pix_fmts; *p != -1; p++) {
               ^
1644.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1645.         const HWAccel *hwaccel;

avtools/avconv.c:1643:24: Loop condition is true. Entering loop body
1641.     int ret;
1642. 
1643.     for (p = pix_fmts; *p != -1; p++) {
                             ^
1644.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1645.         const HWAccel *hwaccel;

avtools/avconv.c:1644:9: 
1642. 
1643.     for (p = pix_fmts; *p != -1; p++) {
1644.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
              ^
1645.         const HWAccel *hwaccel;
1646. 

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)

avtools/avconv.c:1647:15: 
1645.         const HWAccel *hwaccel;
1646. 
1647.         if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
                    ^
1648.             break;
1649. 
