Parameter must be an array

Hi,

In my error log there are several lines every day that says:

[05-Apr-2019 13:16:53 UTC] PHP Warning: count(): Parameter must be an array or an object that implements Countable in /home/deurell/public_html/wp-content/plugins/wp-defender/app/module/ip-lockout/controller/main.php on line 620

What’s wrong and how to fix it?

Thank you, Stina