libavformat/rtsp.c:907: error: Null Dereference
  pointer `st` last assigned on line 898 could be null and is dereferenced at line 907, column 48.

libavformat/rtsp.c:894:1: start of procedure rtsp_open_transport_ctx()
892. }
893. 
894. static int
     ^
895. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
896. {

libavformat/rtsp.c:897:5: 
895. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
896. {
897.     RTSPState *rt = s->priv_data;
         ^
898.     AVStream *st = NULL;
899. 

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

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

libavformat/rtsp.c:903:10: Taking true branch
901.     if (rtsp_st->stream_index >= 0)
902.         st = s->streams[rtsp_st->stream_index];
903.     if (!st)
              ^
904.         s->ctx_flags |= AVFMTCTX_NOHEADER;
905. 

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

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

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