libavformat/rtsp.c:670: error: Null Dereference
  pointer `st` last assigned on line 657 could be null and is dereferenced at line 670, column 56.

libavformat/rtsp.c:654:1: start of procedure rtsp_open_transport_ctx()
652. }
653. 
654. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
     ^
655. {
656.     RTSPState *rt = s->priv_data;

libavformat/rtsp.c:656:5: 
654. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
655. {
656.     RTSPState *rt = s->priv_data;
         ^
657.     AVStream *st = NULL;
658. 

libavformat/rtsp.c:657:5: 
655. {
656.     RTSPState *rt = s->priv_data;
657.     AVStream *st = NULL;
         ^
658. 
659.     /* open the RTP context */

libavformat/rtsp.c:660:9: Taking false branch
658. 
659.     /* open the RTP context */
660.     if (rtsp_st->stream_index >= 0)
             ^
661.         st = s->streams[rtsp_st->stream_index];
662.     if (!st)

libavformat/rtsp.c:662:10: Taking true branch
660.     if (rtsp_st->stream_index >= 0)
661.         st = s->streams[rtsp_st->stream_index];
662.     if (!st)
              ^
663.         s->ctx_flags |= AVFMTCTX_NOHEADER;
664. 

libavformat/rtsp.c:663:9: 
661.         st = s->streams[rtsp_st->stream_index];
662.     if (!st)
663.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
664. 
665.     if (s->oformat) {

libavformat/rtsp.c:665:9: Taking false branch
663.         s->ctx_flags |= AVFMTCTX_NOHEADER;
664. 
665.     if (s->oformat) {
             ^
666.         rtsp_st->transport_priv = rtsp_rtp_mux_open(s, st, rtsp_st->rtp_handle);
667.         /* Ownage of rtp_handle is passed to the rtp mux context */

libavformat/rtsp.c:669:16: Taking true branch
667.         /* Ownage of rtp_handle is passed to the rtp mux context */
668.         rtsp_st->rtp_handle = NULL;
669.     } else if (rt->transport == RTSP_TRANSPORT_RDT)
                    ^
670.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
671.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:670:9: 
668.         rtsp_st->rtp_handle = NULL;
669.     } else if (rt->transport == RTSP_TRANSPORT_RDT)
670.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
671.                                             rtsp_st->dynamic_protocol_context,
672.                                             rtsp_st->dynamic_handler);
