libavformat/rtsp.c:610: error: Null Dereference
  pointer `st` last assigned on line 601 could be null and is dereferenced at line 610, column 56.

libavformat/rtsp.c:598:1: start of procedure rtsp_open_transport_ctx()
596. }
597. 
598. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
     ^
599. {
600.     RTSPState *rt = s->priv_data;

libavformat/rtsp.c:600:5: 
598. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
599. {
600.     RTSPState *rt = s->priv_data;
         ^
601.     AVStream *st = NULL;
602. 

libavformat/rtsp.c:601:5: 
599. {
600.     RTSPState *rt = s->priv_data;
601.     AVStream *st = NULL;
         ^
602. 
603.     /* open the RTP context */

libavformat/rtsp.c:604:9: Taking false branch
602. 
603.     /* open the RTP context */
604.     if (rtsp_st->stream_index >= 0)
             ^
605.         st = s->streams[rtsp_st->stream_index];
606.     if (!st)

libavformat/rtsp.c:606:10: Taking true branch
604.     if (rtsp_st->stream_index >= 0)
605.         st = s->streams[rtsp_st->stream_index];
606.     if (!st)
              ^
607.         s->ctx_flags |= AVFMTCTX_NOHEADER;
608. 

libavformat/rtsp.c:607:9: 
605.         st = s->streams[rtsp_st->stream_index];
606.     if (!st)
607.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
608. 
609.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:609:9: Taking true branch
607.         s->ctx_flags |= AVFMTCTX_NOHEADER;
608. 
609.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
610.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
611.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:610:9: 
608. 
609.     if (rt->transport == RTSP_TRANSPORT_RDT)
610.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
611.                                             rtsp_st->dynamic_protocol_context,
612.                                             rtsp_st->dynamic_handler);
