avconv.c:1813: error: Null Dereference
  pointer `ist` last assigned on line 1811 could be null and is dereferenced at line 1813, column 34.

avconv.c:1808:1: start of procedure init_output_stream_streamcopy()
1806. }
1807. 
1808. static int init_output_stream_streamcopy(OutputStream *ost)
      ^
1809. {
1810.     OutputFile *of = output_files[ost->file_index];

avconv.c:1810:5: 
1808. static int init_output_stream_streamcopy(OutputStream *ost)
1809. {
1810.     OutputFile *of = output_files[ost->file_index];
          ^
1811.     InputStream *ist = get_input_stream(ost);
1812.     AVCodecParameters *par_dst = ost->st->codecpar;

avconv.c:1811:5: 
1809. {
1810.     OutputFile *of = output_files[ost->file_index];
1811.     InputStream *ist = get_input_stream(ost);
          ^
1812.     AVCodecParameters *par_dst = ost->st->codecpar;
1813.     AVCodecParameters *par_src = ist->st->codecpar;

avconv.c:1699:1: start of procedure get_input_stream()
  1697. }
  1698. 
  1699. static InputStream *get_input_stream(OutputStream *ost)
        ^
  1700. {
  1701.     if (ost->source_index >= 0)

avconv.c:1701:9: Taking false branch
  1699. static InputStream *get_input_stream(OutputStream *ost)
  1700. {
  1701.     if (ost->source_index >= 0)
                ^
  1702.         return input_streams[ost->source_index];
  1703. 

avconv.c:1704:9: Taking true branch
  1702.         return input_streams[ost->source_index];
  1703. 
  1704.     if (ost->filter) {
                ^
  1705.         FilterGraph *fg = ost->filter->graph;
  1706.         int i;

avconv.c:1705:9: 
  1703. 
  1704.     if (ost->filter) {
  1705.         FilterGraph *fg = ost->filter->graph;
                ^
  1706.         int i;
  1707. 

avconv.c:1708:14: 
  1706.         int i;
  1707. 
  1708.         for (i = 0; i < fg->nb_inputs; i++)
                     ^
  1709.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1710.                 return fg->inputs[i]->ist;

avconv.c:1708:21: Loop condition is true. Entering loop body
  1706.         int i;
  1707. 
  1708.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1709.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1710.                 return fg->inputs[i]->ist;

avconv.c:1709:17: Taking false branch
  1707. 
  1708.         for (i = 0; i < fg->nb_inputs; i++)
  1709.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
                        ^
  1710.                 return fg->inputs[i]->ist;
  1711.     }

avconv.c:1708:40: 
  1706.         int i;
  1707. 
  1708.         for (i = 0; i < fg->nb_inputs; i++)
                                               ^
  1709.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1710.                 return fg->inputs[i]->ist;

avconv.c:1708:21: Loop condition is false. Leaving loop
  1706.         int i;
  1707. 
  1708.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1709.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1710.                 return fg->inputs[i]->ist;

avconv.c:1713:5: 
  1711.     }
  1712. 
  1713.     return NULL;
            ^
  1714. }
  1715. 

avconv.c:1714:1: return from a call to get_input_stream
  1712. 
  1713.     return NULL;
  1714. }
        ^
  1715. 
  1716. /* open the muxer when all the streams are initialized */

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

avconv.c:1813:5: 
1811.     InputStream *ist = get_input_stream(ost);
1812.     AVCodecParameters *par_dst = ost->st->codecpar;
1813.     AVCodecParameters *par_src = ist->st->codecpar;
          ^
1814.     AVRational sar;
1815.     uint32_t codec_tag = par_dst->codec_tag;
