libavformat/rtsp.c:919: error: Null Dereference
  pointer `st` last assigned on line 910 could be null and is dereferenced at line 919, column 56.

libavformat/rtsp.c:906:1: start of procedure rtsp_open_transport_ctx()
904. }
905. 
906. static int
     ^
907. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
908. {

libavformat/rtsp.c:909:5: 
907. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
908. {
909.     RTSPState *rt = s->priv_data;
         ^
910.     AVStream *st = NULL;
911. 

libavformat/rtsp.c:910:5: 
908. {
909.     RTSPState *rt = s->priv_data;
910.     AVStream *st = NULL;
         ^
911. 
912.     /* open the RTP context */

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

libavformat/rtsp.c:915:10: Taking true branch
913.     if (rtsp_st->stream_index >= 0)
914.         st = s->streams[rtsp_st->stream_index];
915.     if (!st)
              ^
916.         s->ctx_flags |= AVFMTCTX_NOHEADER;
917. 

libavformat/rtsp.c:916:9: 
914.         st = s->streams[rtsp_st->stream_index];
915.     if (!st)
916.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
917. 
918.     if (rt->transport == RTSP_TRANSPORT_RDT)

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

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