文档中说在SAE专有配置Conf/config_sae.php文件中定义如下代码：
<?php
return array( 'TMPL_PARSE_STRING'=>array( '/Public/upload' => $st->getUrl('public','upload'),
));
但是添加配置之后
Fatal error: Call to a member function getUrl() on a non-object in Application/Common/Conf/config_sae.php on line 3
报错了如何解决？？？？