libavformat/rtsp.c:693: error: Null Dereference
  pointer `st` last assigned on line 680 could be null and is dereferenced at line 693, column 56.

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

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

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

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

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

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

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

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

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