Mysql Error

When a user registers he gets this error:

Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: Access denied for user ”@’localhost’ (using password: NO) in /users/mrjoki007/www/wordpress_jokibot/wp-content/plugins/pie-register/classes/base.php on line 798

Warning: mysql_real_escape_string() [function.mysql-real-escape-string]: A link to the server could not be established in /users/mrjoki007/www/wordpress_jokibot/wp-content/plugins/pie-register/classes/base.php on line 798

Dont know why this happens

~MrJoki007

https://ww.wp.xz.cn/plugins/pie-register/