avconv.c:1815: error: Null Dereference
  pointer `ist` last assigned on line 1813 could be null and is dereferenced at line 1815, column 34.

avconv.c:1810:1: start of procedure init_output_stream_streamcopy()
1808. }
1809. 
1810. static int init_output_stream_streamcopy(OutputStream *ost)
      ^
1811. {
1812.     OutputFile *of = output_files[ost->file_index];

avconv.c:1812:5: 
1810. static int init_output_stream_streamcopy(OutputStream *ost)
1811. {
1812.     OutputFile *of = output_files[ost->file_index];
          ^
1813.     InputStream *ist = get_input_stream(ost);
1814.     AVCodecParameters *par_dst = ost->st->codecpar;

avconv.c:1813:5: 
1811. {
1812.     OutputFile *of = output_files[ost->file_index];
1813.     InputStream *ist = get_input_stream(ost);
          ^
1814.     AVCodecParameters *par_dst = ost->st->codecpar;
1815.     AVCodecParameters *par_src = ist->st->codecpar;

avconv.c:1701:1: start of procedure get_input_stream()
  1699. }
  1700. 
  1701. static InputStream *get_input_stream(OutputStream *ost)
        ^
  1702. {
  1703.     if (ost->source_index >= 0)

avconv.c:1703:9: Taking false branch
  1701. static InputStream *get_input_stream(OutputStream *ost)
  1702. {
  1703.     if (ost->source_index >= 0)
                ^
  1704.         return input_streams[ost->source_index];
  1705. 

avconv.c:1706:9: Taking true branch
  1704.         return input_streams[ost->source_index];
  1705. 
  1706.     if (ost->filter) {
                ^
  1707.         FilterGraph *fg = ost->filter->graph;
  1708.         int i;

avconv.c:1707:9: 
  1705. 
  1706.     if (ost->filter) {
  1707.         FilterGraph *fg = ost->filter->graph;
                ^
  1708.         int i;
  1709. 

avconv.c:1710:14: 
  1708.         int i;
  1709. 
  1710.         for (i = 0; i < fg->nb_inputs; i++)
                     ^
  1711.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1712.                 return fg->inputs[i]->ist;

avconv.c:1710:21: Loop condition is true. Entering loop body
  1708.         int i;
  1709. 
  1710.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1711.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1712.                 return fg->inputs[i]->ist;

avconv.c:1711:17: Taking false branch
  1709. 
  1710.         for (i = 0; i < fg->nb_inputs; i++)
  1711.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
                        ^
  1712.                 return fg->inputs[i]->ist;
  1713.     }

avconv.c:1710:40: 
  1708.         int i;
  1709. 
  1710.         for (i = 0; i < fg->nb_inputs; i++)
                                               ^
  1711.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1712.                 return fg->inputs[i]->ist;

avconv.c:1710:21: Loop condition is false. Leaving loop
  1708.         int i;
  1709. 
  1710.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1711.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1712.                 return fg->inputs[i]->ist;

avconv.c:1715:5: 
  1713.     }
  1714. 
  1715.     return NULL;
            ^
  1716. }
  1717. 

avconv.c:1716:1: return from a call to get_input_stream
  1714. 
  1715.     return NULL;
  1716. }
        ^
  1717. 
  1718. /* open the muxer when all the streams are initialized */

avconv.c:1814:5: 
1812.     OutputFile *of = output_files[ost->file_index];
1813.     InputStream *ist = get_input_stream(ost);
1814.     AVCodecParameters *par_dst = ost->st->codecpar;
          ^
1815.     AVCodecParameters *par_src = ist->st->codecpar;
1816.     AVRational sar;

avconv.c:1815:5: 
1813.     InputStream *ist = get_input_stream(ost);
1814.     AVCodecParameters *par_dst = ost->st->codecpar;
1815.     AVCodecParameters *par_src = ist->st->codecpar;
          ^
1816.     AVRational sar;
1817.     uint32_t codec_tag = par_dst->codec_tag;
