libavformat/rtsp.c:694: error: Null Dereference
  pointer `st` last assigned on line 681 could be null and is dereferenced at line 694, column 56.

libavformat/rtsp.c:678:1: start of procedure rtsp_open_transport_ctx()
676. }
677. 
678. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
     ^
679. {
680.     RTSPState *rt = s->priv_data;

libavformat/rtsp.c:680:5: 
678. static int rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
679. {
680.     RTSPState *rt = s->priv_data;
         ^
681.     AVStream *st = NULL;
682. 

libavformat/rtsp.c:681:5: 
679. {
680.     RTSPState *rt = s->priv_data;
681.     AVStream *st = NULL;
         ^
682. 
683.     /* open the RTP context */

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

libavformat/rtsp.c:686:10: Taking true branch
684.     if (rtsp_st->stream_index >= 0)
685.         st = s->streams[rtsp_st->stream_index];
686.     if (!st)
              ^
687.         s->ctx_flags |= AVFMTCTX_NOHEADER;
688. 

libavformat/rtsp.c:687:9: 
685.         st = s->streams[rtsp_st->stream_index];
686.     if (!st)
687.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
688. 
689.     if (s->oformat) {

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

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

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