Use != null to handle undefined

lib/browser/api/dialog.js

@@ -19,7 +19,7 @@ const messageBoxOptions = {
 }
 
 const parseArgs = function (window, options, callback, ...args) {
-  if (window !== null && window.constructor !== BrowserWindow) {
+  if (window != null && window.constructor !== BrowserWindow) {
     // Shift.
     [callback, options, window] = [options, window, null]
   }