disable warnings doesn't work

I didn’t renew my pro license yet. Thus I get this message:

Due to some inevitable changes to some code in Events Manager, it is necessary to use Pro 2.3.7.7 or later. We have disabled the Pro plugin as a safety precaution.
Click here for detailed information about this change, which includes some simple instructions for fixing older versions of Pro without requiring an update.
Only Administrators see this message. To hide critical messages and prevent this safety measure, you can add define('EMP_DISABLE_CRITICAL_WARNINGS', true); as a new line in your wp-config.php file.

So I add

define('EMP_DISABLE_CRITICAL_WARNINGS', true);

to wp-config.php and I get this error.

Fatal error: Cannot make static method EM_Object::get_default_search() non static in class EM_Coupons in /home/freeride/domains/freerides.org/public_html/wp-content/plugins/events-manager-pro/add-ons/coupons/coupons.php on line 663

https://wordpress.org/plugins/events-manager/