This error message frequently appear", eval()'d code on line 3

Hi,

the content area will be a blank page, it will show the below area message

Cannot use object of type WP_Error as array in /home/mywebsite/public_html/wp-content/plugins/php-code-for-posts/PHPPostCode.php(85) : eval()’d code on line 3

how do i solve ?
thanks

https://wordpress.org/plugins/php-code-for-posts/