libavformat/rtsp.c:904: error: Null Dereference
  pointer `st` last assigned on line 895 could be null and is dereferenced at line 904, column 48.

libavformat/rtsp.c:891:1: start of procedure rtsp_open_transport_ctx()
889. }
890. 
891. static int
     ^
892. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
893. {

libavformat/rtsp.c:894:5: 
892. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
893. {
894.     RTSPState *rt = s->priv_data;
         ^
895.     AVStream *st = NULL;
896. 

libavformat/rtsp.c:895:5: 
893. {
894.     RTSPState *rt = s->priv_data;
895.     AVStream *st = NULL;
         ^
896. 
897.     /* open the RTP context */

libavformat/rtsp.c:898:9: Taking false branch
896. 
897.     /* open the RTP context */
898.     if (rtsp_st->stream_index >= 0)
             ^
899.         st = s->streams[rtsp_st->stream_index];
900.     if (!st)

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

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

libavformat/rtsp.c:903:9: Taking true branch
901.         s->ctx_flags |= AVFMTCTX_NOHEADER;
902. 
903.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
904.         rtsp_st->tx_ctx = ff_rdt_parse_open(s, st->index,
905.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:904:9: 
902. 
903.     if (rt->transport == RTSP_TRANSPORT_RDT)
904.         rtsp_st->tx_ctx = ff_rdt_parse_open(s, st->index,
             ^
905.                                             rtsp_st->dynamic_protocol_context,
906.                                             rtsp_st->dynamic_handler);
