avconv.c:1832: error: Null Dereference
  pointer `ist` last assigned on line 1830 could be null and is dereferenced at line 1832, column 34.

avconv.c:1827:1: start of procedure init_output_stream_streamcopy()
1825. }
1826. 
1827. static int init_output_stream_streamcopy(OutputStream *ost)
      ^
1828. {
1829.     OutputFile *of = output_files[ost->file_index];

avconv.c:1829:5: 
1827. static int init_output_stream_streamcopy(OutputStream *ost)
1828. {
1829.     OutputFile *of = output_files[ost->file_index];
          ^
1830.     InputStream *ist = get_input_stream(ost);
1831.     AVCodecParameters *par_dst = ost->st->codecpar;

avconv.c:1830:5: 
1828. {
1829.     OutputFile *of = output_files[ost->file_index];
1830.     InputStream *ist = get_input_stream(ost);
          ^
1831.     AVCodecParameters *par_dst = ost->st->codecpar;
1832.     AVCodecParameters *par_src = ist->st->codecpar;

avconv.c:1728:1: start of procedure get_input_stream()
  1726. }
  1727. 
  1728. static InputStream *get_input_stream(OutputStream *ost)
        ^
  1729. {
  1730.     if (ost->source_index >= 0)

avconv.c:1730:9: Taking false branch
  1728. static InputStream *get_input_stream(OutputStream *ost)
  1729. {
  1730.     if (ost->source_index >= 0)
                ^
  1731.         return input_streams[ost->source_index];
  1732. 

avconv.c:1733:9: Taking true branch
  1731.         return input_streams[ost->source_index];
  1732. 
  1733.     if (ost->filter) {
                ^
  1734.         FilterGraph *fg = ost->filter->graph;
  1735.         int i;

avconv.c:1734:9: 
  1732. 
  1733.     if (ost->filter) {
  1734.         FilterGraph *fg = ost->filter->graph;
                ^
  1735.         int i;
  1736. 

avconv.c:1737:14: 
  1735.         int i;
  1736. 
  1737.         for (i = 0; i < fg->nb_inputs; i++)
                     ^
  1738.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1739.                 return fg->inputs[i]->ist;

avconv.c:1737:21: Loop condition is true. Entering loop body
  1735.         int i;
  1736. 
  1737.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1738.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1739.                 return fg->inputs[i]->ist;

avconv.c:1738:17: Taking false branch
  1736. 
  1737.         for (i = 0; i < fg->nb_inputs; i++)
  1738.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
                        ^
  1739.                 return fg->inputs[i]->ist;
  1740.     }

avconv.c:1737:40: 
  1735.         int i;
  1736. 
  1737.         for (i = 0; i < fg->nb_inputs; i++)
                                               ^
  1738.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1739.                 return fg->inputs[i]->ist;

avconv.c:1737:21: Loop condition is false. Leaving loop
  1735.         int i;
  1736. 
  1737.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1738.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1739.                 return fg->inputs[i]->ist;

avconv.c:1742:5: 
  1740.     }
  1741. 
  1742.     return NULL;
            ^
  1743. }
  1744. 

avconv.c:1743:1: return from a call to get_input_stream
  1741. 
  1742.     return NULL;
  1743. }
        ^
  1744. 
  1745. /* open the muxer when all the streams are initialized */

avconv.c:1831:5: 
1829.     OutputFile *of = output_files[ost->file_index];
1830.     InputStream *ist = get_input_stream(ost);
1831.     AVCodecParameters *par_dst = ost->st->codecpar;
          ^
1832.     AVCodecParameters *par_src = ist->st->codecpar;
1833.     AVRational sar;

avconv.c:1832:5: 
1830.     InputStream *ist = get_input_stream(ost);
1831.     AVCodecParameters *par_dst = ost->st->codecpar;
1832.     AVCodecParameters *par_src = ist->st->codecpar;
          ^
1833.     AVRational sar;
1834.     uint32_t codec_tag = par_dst->codec_tag;
