libavformat/rtsp.c:917: error: Null Dereference
  pointer `st` last assigned on line 908 could be null and is dereferenced at line 917, column 56.

libavformat/rtsp.c:904:1: start of procedure rtsp_open_transport_ctx()
902. }
903. 
904. static int
     ^
905. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
906. {

libavformat/rtsp.c:907:5: 
905. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
906. {
907.     RTSPState *rt = s->priv_data;
         ^
908.     AVStream *st = NULL;
909. 

libavformat/rtsp.c:908:5: 
906. {
907.     RTSPState *rt = s->priv_data;
908.     AVStream *st = NULL;
         ^
909. 
910.     /* open the RTP context */

libavformat/rtsp.c:911:9: Taking false branch
909. 
910.     /* open the RTP context */
911.     if (rtsp_st->stream_index >= 0)
             ^
912.         st = s->streams[rtsp_st->stream_index];
913.     if (!st)

libavformat/rtsp.c:913:10: Taking true branch
911.     if (rtsp_st->stream_index >= 0)
912.         st = s->streams[rtsp_st->stream_index];
913.     if (!st)
              ^
914.         s->ctx_flags |= AVFMTCTX_NOHEADER;
915. 

libavformat/rtsp.c:914:9: 
912.         st = s->streams[rtsp_st->stream_index];
913.     if (!st)
914.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
915. 
916.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:916:9: Taking true branch
914.         s->ctx_flags |= AVFMTCTX_NOHEADER;
915. 
916.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
917.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
918.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:917:9: 
915. 
916.     if (rt->transport == RTSP_TRANSPORT_RDT)
917.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
918.                                             rtsp_st->dynamic_protocol_context,
919.                                             rtsp_st->dynamic_handler);
