Fix no-crypto build

no-crypto.go

@@ -2,6 +2,10 @@
 
 package main
 
+import (
+	"errors"
+)
+
 func NewCryptoHelper(bridge *Bridge) Crypto {
 	if !bridge.Config.Bridge.Encryption.Allow {
 		bridge.Log.Warnln("Bridge built without end-to-bridge encryption, but encryption is enabled in config")