fixed: 调用系统is_null方法

Gameserver/Amfphp/base/Resp.php

@@ -97,8 +97,8 @@ class Resp extends Object_ext {
     public static function AddEvent($name, $arg1, $arg2) {
         self::$ext_events[] = array(
             'name' => $name,
-            'arg1' => isNull($arg1) ? ObjectInit() : $arg1,
-            'arg2' => isNull($arg2) ? ObjectInit() : $arg2
+            'arg1' => is_null($arg1) ? ObjectInit() : $arg1,
+            'arg2' => is_null($arg2) ? ObjectInit() : $arg2
         );
     }