Warning on Dashboard after updated to v5.0.6

After updating to the latest version of the plugin, there is a PHP warning on my dashboard that reads:
Warning: array_key_exists(): The first argument should be either a string or an integer in /home/mich9349/public_html/wp-content/plugins/advanced-access-manager/Application/Core/API.php on line 218

That line is:
return (array_key_exists($cap, $caps) ? true : false);