avconv.c:1826: error: Null Dereference
  pointer `ist` last assigned on line 1824 could be null and is dereferenced at line 1826, column 34.

avconv.c:1821:1: start of procedure init_output_stream_streamcopy()
1819. }
1820. 
1821. static int init_output_stream_streamcopy(OutputStream *ost)
      ^
1822. {
1823.     OutputFile *of = output_files[ost->file_index];

avconv.c:1823:5: 
1821. static int init_output_stream_streamcopy(OutputStream *ost)
1822. {
1823.     OutputFile *of = output_files[ost->file_index];
          ^
1824.     InputStream *ist = get_input_stream(ost);
1825.     AVCodecParameters *par_dst = ost->st->codecpar;

avconv.c:1824:5: 
1822. {
1823.     OutputFile *of = output_files[ost->file_index];
1824.     InputStream *ist = get_input_stream(ost);
          ^
1825.     AVCodecParameters *par_dst = ost->st->codecpar;
1826.     AVCodecParameters *par_src = ist->st->codecpar;

avconv.c:1712:1: start of procedure get_input_stream()
  1710. }
  1711. 
  1712. static InputStream *get_input_stream(OutputStream *ost)
        ^
  1713. {
  1714.     if (ost->source_index >= 0)

avconv.c:1714:9: Taking false branch
  1712. static InputStream *get_input_stream(OutputStream *ost)
  1713. {
  1714.     if (ost->source_index >= 0)
                ^
  1715.         return input_streams[ost->source_index];
  1716. 

avconv.c:1717:9: Taking true branch
  1715.         return input_streams[ost->source_index];
  1716. 
  1717.     if (ost->filter) {
                ^
  1718.         FilterGraph *fg = ost->filter->graph;
  1719.         int i;

avconv.c:1718:9: 
  1716. 
  1717.     if (ost->filter) {
  1718.         FilterGraph *fg = ost->filter->graph;
                ^
  1719.         int i;
  1720. 

avconv.c:1721:14: 
  1719.         int i;
  1720. 
  1721.         for (i = 0; i < fg->nb_inputs; i++)
                     ^
  1722.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1723.                 return fg->inputs[i]->ist;

avconv.c:1721:21: Loop condition is true. Entering loop body
  1719.         int i;
  1720. 
  1721.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1722.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1723.                 return fg->inputs[i]->ist;

avconv.c:1722:17: Taking false branch
  1720. 
  1721.         for (i = 0; i < fg->nb_inputs; i++)
  1722.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
                        ^
  1723.                 return fg->inputs[i]->ist;
  1724.     }

avconv.c:1721:40: 
  1719.         int i;
  1720. 
  1721.         for (i = 0; i < fg->nb_inputs; i++)
                                               ^
  1722.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1723.                 return fg->inputs[i]->ist;

avconv.c:1721:21: Loop condition is false. Leaving loop
  1719.         int i;
  1720. 
  1721.         for (i = 0; i < fg->nb_inputs; i++)
                            ^
  1722.             if (fg->inputs[i]->ist->dec_ctx->codec_type == ost->enc_ctx->codec_type)
  1723.                 return fg->inputs[i]->ist;

avconv.c:1726:5: 
  1724.     }
  1725. 
  1726.     return NULL;
            ^
  1727. }
  1728. 

avconv.c:1727:1: return from a call to get_input_stream
  1725. 
  1726.     return NULL;
  1727. }
        ^
  1728. 
  1729. /* open the muxer when all the streams are initialized */

avconv.c:1825:5: 
1823.     OutputFile *of = output_files[ost->file_index];
1824.     InputStream *ist = get_input_stream(ost);
1825.     AVCodecParameters *par_dst = ost->st->codecpar;
          ^
1826.     AVCodecParameters *par_src = ist->st->codecpar;
1827.     AVRational sar;

avconv.c:1826:5: 
1824.     InputStream *ist = get_input_stream(ost);
1825.     AVCodecParameters *par_dst = ost->st->codecpar;
1826.     AVCodecParameters *par_src = ist->st->codecpar;
          ^
1827.     AVRational sar;
1828.     uint32_t codec_tag = par_dst->codec_tag;
