Init vars with a value if none is provided

core/js/js.js

@@ -234,6 +234,7 @@ var OC={
 	 */
 	generateUrl: function(url, params) {
 		var _build = function (text, vars) {
+			var vars = vars || [];
 			return text.replace(/{([^{}]*)}/g,
 				function (a, b) {
 					var r = vars[b];

core/js/tests/specs/coreSpec.js

@@ -376,6 +376,9 @@ describe('Core base tests', function() {
 		it('substitutes parameters', function() {
 			expect(OC.generateUrl('apps/files/download{file}', {file: '/Welcome.txt'})).toEqual(OC.webroot + '/index.php/apps/files/download/Welcome.txt');
 		});
+		it('doesnt error out with no params provided', function  () {
+			expect(OC.generateUrl('apps/files/download{file}')).toEqual(OC.webroot + '/index.php/apps/files/download{file}');
+		});
 	});
 	describe('Main menu mobile toggle', function() {
 		var clock;