add conditional for menu.popup(window, callback)

lib/browser/api/menu.js

@@ -58,8 +58,9 @@ Menu.prototype.popup = function (window, x, y, positioningItem) {
     callback = newPosition
   }
 
-  // menu.popup({})
-  if (window != null && window.constructor === Object) {
+  // menu.popup({}) || menu.popup(window, callback)
+  if ((window != null && window.constructor === Object) ||
+      (x && typeof x === 'function')) {
     opts = window
     callback = arguments[1]
   // menu.popup(window, {})