fix bug

web/server.go

@@ -59,6 +59,8 @@ func NewServer(clock *derby.DerbyClock, events <-chan derby.Event, dbPath string
 		events:          events,
 		clients:         make(map[chan string]bool),
 		clientsMux:      sync.Mutex{},
+		adminclients:    make(map[chan string]bool),
+		adminclientsMux: sync.Mutex{},
 		port:            port,
 		shutdown:        make(chan struct{}),
 		logger:          logger,