libavformat/rtsp.c:692: error: Null Dereference
  pointer `st` last assigned on line 679 could be null and is dereferenced at line 692, column 56.

libavformat/rtsp.c:676:1: start of procedure rtsp_open_transport_ctx()
674. }
675. 
676. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
     ^
677. {
678.     RTSPState *rt = s->priv_data;

libavformat/rtsp.c:678:5: 
676. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
677. {
678.     RTSPState *rt = s->priv_data;
         ^
679.     AVStream *st = NULL;
680. 

libavformat/rtsp.c:679:5: 
677. {
678.     RTSPState *rt = s->priv_data;
679.     AVStream *st = NULL;
         ^
680. 
681.     /* open the RTP context */

libavformat/rtsp.c:682:9: Taking false branch
680. 
681.     /* open the RTP context */
682.     if (rtsp_st->stream_index >= 0)
             ^
683.         st = s->streams[rtsp_st->stream_index];
684.     if (!st)

libavformat/rtsp.c:684:10: Taking true branch
682.     if (rtsp_st->stream_index >= 0)
683.         st = s->streams[rtsp_st->stream_index];
684.     if (!st)
              ^
685.         s->ctx_flags |= AVFMTCTX_NOHEADER;
686. 

libavformat/rtsp.c:685:9: 
683.         st = s->streams[rtsp_st->stream_index];
684.     if (!st)
685.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
686. 
687.     if (s->oformat) {

libavformat/rtsp.c:687:9: Taking false branch
685.         s->ctx_flags |= AVFMTCTX_NOHEADER;
686. 
687.     if (s->oformat) {
             ^
688.         rtsp_st->transport_priv = rtsp_rtp_mux_open(s, st, rtsp_st->rtp_handle);
689.         /* Ownage of rtp_handle is passed to the rtp mux context */

libavformat/rtsp.c:691:16: Taking true branch
689.         /* Ownage of rtp_handle is passed to the rtp mux context */
690.         rtsp_st->rtp_handle = NULL;
691.     } else if (rt->transport == RTSP_TRANSPORT_RDT)
                    ^
692.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
693.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:692:9: 
690.         rtsp_st->rtp_handle = NULL;
691.     } else if (rt->transport == RTSP_TRANSPORT_RDT)
692.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
693.                                             rtsp_st->dynamic_protocol_context,
694.                                             rtsp_st->dynamic_handler);
