discuz3.4安装插件报错：Cannot use string offset as an array

环境：PHP7.1以上

解决办法：

文件source/function/function_plugin.php

搜索：foreach($vars as $key => $var) {

后面插入代码

 if(!$_G['cache']['pluginlanguage_system'])
 $_G['cache']['pluginlanguage_system']=array();