Update

vendor/tailscale.com/feature/portmapper/portmapper.go

@@ -1,4 +1,4 @@
-// Copyright (c) Tailscale Inc & AUTHORS
+// Copyright (c) Tailscale Inc & contributors
 // SPDX-License-Identifier: BSD-3-Clause
 
 // Package portmapper registers support for NAT-PMP, PCP, and UPnP port
@@ -15,7 +15,9 @@ import (
 )
 
 func init() {
-	feature.Register("portmapper")
+	if !feature.Register("portmapper") {
+		return
+	}
 	portmappertype.HookNewPortMapper.Set(newPortMapper)
 }