minor #5541 RuleSet - disallow null usage to disable the rule (keradus)
minor #5541 RuleSet - disallow null usage to disable the rule (keradus)

This PR was merged into the 3.0 branch.

Discussion
----------

RuleSet - disallow null usage to disable the rule

Awaits for:
- [x] #5540

Commits
-------

fa87aebac RuleSet - disallow null usage to disable the rule

SpacePossum/PHP-CS-Fixer,keradus/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,keradus/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,FriendsOfPHP/PHP-CS-Fixer,gharlan/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,kubawerlos/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer,SpacePossum/PHP-CS-Fixer,Slamdunk/PHP-CS-Fixer