rename lang to language, because req.lang is not defined.

src/server/routes/login.js

@@ -141,7 +141,7 @@ module.exports = function(crowi, app) {
 
   actions.register = function(req, res) {
     var googleAuth = require('../util/googleAuth')(config);
-    var lang= req.lang || User.LANG_EN_US;
+    var lang = req.language || User.LANG_EN_US;
 
     // ログイン済みならさようなら
     if (req.user) {