fix: make options more compatibility

Author: dead-horse

lib/application.js

@@ -44,13 +44,14 @@ module.exports = class Application extends Emitter {
     *
     */
 
-  constructor(options = {}) {
+  constructor(options) {
     super();
+    options = options || {};
     this.proxy = options.proxy || false;
-    this.middleware = [];
     this.subdomainOffset = options.subdomainOffset || 2;
     this.env = options.env || process.env.NODE_ENV || 'development';
-    this.keys = options.keys || undefined;
+    if (options.keys) this.keys = options.keys;
+    this.middleware = [];
     this.context = Object.create(context);
     this.request = Object.create(request);
     this.response = Object.create(response);