Warnings after upgrade to PHP 7.2 in error.log: Use of undefined constant AUTH_KEY in Kleo theme

Hi,

Since the upgrade from PHP 5.6 to PHP 7.2 I see the following two warnings in the Apache error.log. There are several such message for every page call. I think that this slows down our site. At the moment we use PHP 7.2 only a test site, but we need to upgrade these days.

PHP Warning:  Use of undefined constant AUTH_KEY – assumed ‘AUTH_KEY’ (this will throw an Error in a future version of PHP) in /vl/www/4sysops/wp-content/themes/kleo/kleo-framework/options/inc/class.redux_instances.php on line 67,

PHP Warning:  Use of undefined constant SECURE_AUTH_KEY – assumed ‘SECURE_AUTH_KEY’ (this will throw an Error in a future version of PHP) in /vl/www/4sysops/wp-content/themes/kleo/kleo-framework/options/inc/class.redux_instances.php on line 67,