WP Debug mode is a setting which can be used in WordPress if you are troubleshooting issues or need to debug your site. This mode will enable logging of activity and errors on your WordPress site.
Whilst this option is very useful, leaving it enabled can slow your site down and also can mean you see server warnings which otherwise would be hidden on your site.
Note: If you are not confident making changes to your WordPress configuration files, we recommend asking your hosting company to make these changes for you. Most good hosts will be happy to do this for you.
To turn off WP Debug, follow these steps
Navigate to your wp-config.php file inside your WordPress directory. This can be accessed via FTP or file manager in your hosting Cpanel.
Open the WP-config.php file
Look for a line that reads:
define('WP_DEBUG', true);
All you need to do is change "true" to "false.
So the line should read:
define('WP_DEBUG', false);
Once you've made this change, save your wp-config.php file and refresh your site, you should see that error disappear.