libavformat/rtsp.c:860: error: Null Dereference
  pointer `st` last assigned on line 851 could be null and is dereferenced at line 860, column 56.

libavformat/rtsp.c:847:1: start of procedure rtsp_open_transport_ctx()
845. }
846. 
847. static int
     ^
848. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
849. {

libavformat/rtsp.c:850:5: 
848. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
849. {
850.     RTSPState *rt = s->priv_data;
         ^
851.     AVStream *st = NULL;
852. 

libavformat/rtsp.c:851:5: 
849. {
850.     RTSPState *rt = s->priv_data;
851.     AVStream *st = NULL;
         ^
852. 
853.     /* open the RTP context */

libavformat/rtsp.c:854:9: Taking false branch
852. 
853.     /* open the RTP context */
854.     if (rtsp_st->stream_index >= 0)
             ^
855.         st = s->streams[rtsp_st->stream_index];
856.     if (!st)

libavformat/rtsp.c:856:10: Taking true branch
854.     if (rtsp_st->stream_index >= 0)
855.         st = s->streams[rtsp_st->stream_index];
856.     if (!st)
              ^
857.         s->ctx_flags |= AVFMTCTX_NOHEADER;
858. 

libavformat/rtsp.c:857:9: 
855.         st = s->streams[rtsp_st->stream_index];
856.     if (!st)
857.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
858. 
859.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:859:9: Taking true branch
857.         s->ctx_flags |= AVFMTCTX_NOHEADER;
858. 
859.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
860.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
861.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:860:9: 
858. 
859.     if (rt->transport == RTSP_TRANSPORT_RDT)
860.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
861.                                             rtsp_st->dynamic_protocol_context,
862.                                             rtsp_st->dynamic_handler);
