array_key_exists throws warning when plugin_settings is false

function add_notices in /includes/classes/wp-maintenance-mode-admin.php
line 548 throws a warning about $this->plugin_settings being false while array_key_exists expects second param to be an array.

might i suggest the following fix:

 if (array_key_exists('general', is_array($this->plugin_settings) ? $this->plugin_settings : []) && ....