libavformat/rtsp.c:880: error: Null Dereference
  pointer `st` last assigned on line 871 could be null and is dereferenced at line 880, column 56.

libavformat/rtsp.c:867:1: start of procedure rtsp_open_transport_ctx()
865. }
866. 
867. static int
     ^
868. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
869. {

libavformat/rtsp.c:870:5: 
868. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
869. {
870.     RTSPState *rt = s->priv_data;
         ^
871.     AVStream *st = NULL;
872. 

libavformat/rtsp.c:871:5: 
869. {
870.     RTSPState *rt = s->priv_data;
871.     AVStream *st = NULL;
         ^
872. 
873.     /* open the RTP context */

libavformat/rtsp.c:874:9: Taking false branch
872. 
873.     /* open the RTP context */
874.     if (rtsp_st->stream_index >= 0)
             ^
875.         st = s->streams[rtsp_st->stream_index];
876.     if (!st)

libavformat/rtsp.c:876:10: Taking true branch
874.     if (rtsp_st->stream_index >= 0)
875.         st = s->streams[rtsp_st->stream_index];
876.     if (!st)
              ^
877.         s->ctx_flags |= AVFMTCTX_NOHEADER;
878. 

libavformat/rtsp.c:877:9: 
875.         st = s->streams[rtsp_st->stream_index];
876.     if (!st)
877.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
878. 
879.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:879:9: Taking true branch
877.         s->ctx_flags |= AVFMTCTX_NOHEADER;
878. 
879.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
880.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
881.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:880:9: 
878. 
879.     if (rt->transport == RTSP_TRANSPORT_RDT)
880.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
881.                                             rtsp_st->dynamic_protocol_context,
882.                                             rtsp_st->dynamic_handler);
