libavformat/rtsp.c:926: error: Null Dereference
  pointer `st` last assigned on line 917 could be null and is dereferenced at line 926, column 56.

libavformat/rtsp.c:913:1: start of procedure rtsp_open_transport_ctx()
911. }
912. 
913. static int
     ^
914. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
915. {

libavformat/rtsp.c:916:5: 
914. rtsp_open_transport_ctx(AVFormatContext *s, RTSPStream *rtsp_st)
915. {
916.     RTSPState *rt = s->priv_data;
         ^
917.     AVStream *st = NULL;
918. 

libavformat/rtsp.c:917:5: 
915. {
916.     RTSPState *rt = s->priv_data;
917.     AVStream *st = NULL;
         ^
918. 
919.     /* open the RTP context */

libavformat/rtsp.c:920:9: Taking false branch
918. 
919.     /* open the RTP context */
920.     if (rtsp_st->stream_index >= 0)
             ^
921.         st = s->streams[rtsp_st->stream_index];
922.     if (!st)

libavformat/rtsp.c:922:10: Taking true branch
920.     if (rtsp_st->stream_index >= 0)
921.         st = s->streams[rtsp_st->stream_index];
922.     if (!st)
              ^
923.         s->ctx_flags |= AVFMTCTX_NOHEADER;
924. 

libavformat/rtsp.c:923:9: 
921.         st = s->streams[rtsp_st->stream_index];
922.     if (!st)
923.         s->ctx_flags |= AVFMTCTX_NOHEADER;
             ^
924. 
925.     if (rt->transport == RTSP_TRANSPORT_RDT)

libavformat/rtsp.c:925:9: Taking true branch
923.         s->ctx_flags |= AVFMTCTX_NOHEADER;
924. 
925.     if (rt->transport == RTSP_TRANSPORT_RDT)
             ^
926.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
927.                                             rtsp_st->dynamic_protocol_context,

libavformat/rtsp.c:926:9: 
924. 
925.     if (rt->transport == RTSP_TRANSPORT_RDT)
926.         rtsp_st->transport_priv = ff_rdt_parse_open(s, st->index,
             ^
927.                                             rtsp_st->dynamic_protocol_context,
928.                                             rtsp_st->dynamic_handler);
