only use passport.authenticate if a strategy url is defined

src/routes/authentication.js

@@ -148,9 +148,11 @@
 				for (var i in login_strategies) {
 					if (login_strategies.hasOwnProperty(i)) {
 						var strategy = login_strategies[i];
+						if (strategy.url) {
 							app.get(strategy.url, passport.authenticate(strategy.name, {
 								scope: strategy.scope
 							}));
+						}
 
 						app.get(strategy.callbackURL, passport.authenticate(strategy.name, {
 							successRedirect: nconf.get('relative_path') + '/',