libavformat/rtsp.c:906: error: Null Dereference
  pointer `st` last assigned on line 897 could be null and is dereferenced at line 906, column 56.

libavformat/rtsp.c:893:1: start of procedure rtsp_open_transport_ctx()
891. }
892. 
893. static int
     ^
894. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
895. {

libavformat/rtsp.c:896:5: 
894. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
895. {
896.     RTSPState *rt = s->priv_data;
         ^
897.     AVStream *st = NULL;
898. 

libavformat/rtsp.c:897:5: 
895. {
896.     RTSPState *rt = s->priv_data;
897.     AVStream *st = NULL;
         ^
898. 
899.     /* open the RTP context */

libavformat/rtsp.c:900:9: Taking false branch
898. 
899.     /* open the RTP context */
900.     if (rtsp_st->stream_index >= 0)
             ^
901.         st = s->streams[rtsp_st->stream_index];
902.     if (!st)

libavformat/rtsp.c:902:10: Taking true branch
900.     if (rtsp_st->stream_index >= 0)
901.         st = s->streams[rtsp_st->stream_index];
902.     if (!st)
              ^
903.         s->ctx_flags |= AVFMTCTX_NOHEADER;
904. 

libavformat/rtsp.c:903:9: 
901.         st = s->streams[rtsp_st->stream_index];
902.     if (!st)
903.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
904. 
905.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:905:9: Taking true branch
903.         s->ctx_flags |= AVFMTCTX_NOHEADER;
904. 
905.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
906.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
907.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:906:9: 
904. 
905.     if (rt->transport == RTSP_TRANSPORT_RDT)
906.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
907.                                             rtsp_st->dynamic_protocol_context,
908.                                             rtsp_st->dynamic_handler);
