PHP Errors

This plugin is producing the following two error warnings:

Warning: explode() expects parameter 2 to be string, array given in /home/tim/www/mainwp/wp-includes/post-template.php on line 992 

Warning: implode(): Invalid arguments passed in /home/tim/www/mainwp/wp-includes/post-template.php on line 1001

https://ww.wp.xz.cn/plugins/s8-private-pages/