avconv.c:1521: error: Null Dereference
  pointer `desc` last assigned on line 1518 could be null and is dereferenced at line 1521, column 15.

avconv.c:1511:1: start of procedure get_format()
1509. }
1510. 
1511. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
      ^
1512. {
1513.     InputStream *ist = s->opaque;

avconv.c:1513:5: 
1511. static enum AVPixelFormat get_format(AVCodecContext *s, const enum AVPixelFormat *pix_fmts)
1512. {
1513.     InputStream *ist = s->opaque;
          ^
1514.     const enum AVPixelFormat *p;
1515.     int ret;

avconv.c:1517:10: 
1515.     int ret;
1516. 
1517.     for (p = pix_fmts; *p != -1; p++) {
               ^
1518.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1519.         const HWAccel *hwaccel;

avconv.c:1517:24: Loop condition is true. Entering loop body
1515.     int ret;
1516. 
1517.     for (p = pix_fmts; *p != -1; p++) {
                             ^
1518.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
1519.         const HWAccel *hwaccel;

avconv.c:1518:9: 
1516. 
1517.     for (p = pix_fmts; *p != -1; p++) {
1518.         const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(*p);
              ^
1519.         const HWAccel *hwaccel;
1520. 

libavutil/pixdesc.c:1703:1: start of procedure av_pix_fmt_desc_get()
  1701. }
  1702. 
  1703. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1704. {
  1705.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1705:9: Taking false branch
  1703. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1704. {
  1705.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1706.         return NULL;
  1707.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1705:24: Taking true branch
  1703. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1704. {
  1705.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1706.         return NULL;
  1707.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1706:9: 
  1704. {
  1705.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1706.         return NULL;
                ^
  1707.     return &av_pix_fmt_descriptors[pix_fmt];
  1708. }

libavutil/pixdesc.c:1708:1: return from a call to av_pix_fmt_desc_get
  1706.         return NULL;
  1707.     return &av_pix_fmt_descriptors[pix_fmt];
  1708. }
        ^
  1709. 
  1710. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

avconv.c:1521:15: 
1519.         const HWAccel *hwaccel;
1520. 
1521.         if (!(desc->flags & AV_PIX_FMT_FLAG_HWACCEL))
                    ^
1522.             break;
1523. 
