libavformat/rtsp.c:620: error: Null Dereference
  pointer `st` last assigned on line 611 could be null and is dereferenced at line 620, column 56.

libavformat/rtsp.c:608:1: start of procedure rtsp_open_transport_ctx()
606. }
607. 
608. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
     ^
609. {
610.     RTSPState *rt = s->priv_data;

libavformat/rtsp.c:610:5: 
608. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
609. {
610.     RTSPState *rt = s->priv_data;
         ^
611.     AVStream *st = NULL;
612. 

libavformat/rtsp.c:611:5: 
609. {
610.     RTSPState *rt = s->priv_data;
611.     AVStream *st = NULL;
         ^
612. 
613.     /* open the RTP context */

libavformat/rtsp.c:614:9: Taking false branch
612. 
613.     /* open the RTP context */
614.     if (rtsp_st->stream_index >= 0)
             ^
615.         st = s->streams[rtsp_st->stream_index];
616.     if (!st)

libavformat/rtsp.c:616:10: Taking true branch
614.     if (rtsp_st->stream_index >= 0)
615.         st = s->streams[rtsp_st->stream_index];
616.     if (!st)
              ^
617.         s->ctx_flags |= AVFMTCTX_NOHEADER;
618. 

libavformat/rtsp.c:617:9: 
615.         st = s->streams[rtsp_st->stream_index];
616.     if (!st)
617.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
618. 
619.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:619:9: Taking true branch
617.         s->ctx_flags |= AVFMTCTX_NOHEADER;
618. 
619.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
620.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
621.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:620:9: 
618. 
619.     if (rt->transport == RTSP_TRANSPORT_RDT)
620.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
621.                                             rtsp_st->dynamic_protocol_context,
622.                                             rtsp_st->dynamic_handler);
