Update Check.php

Return null if no ignored plugins setting exists (if setting is `null` then it disappears from the database, thus you get a PHP notice when trying to grab it.)

src/Check.php

@@ -27,6 +27,9 @@ private function setting($setting) {
 
 		$nagios_settings = get_option('nagios-settings', ["nagios_server_ip" => "127.0.0.1", "ignored_plugins"=>NULL]);
 		$this->ip_address = $nagios_settings['nagios_server_ip'];
+		if ($setting === "ignored_plugins" && !isset($nagios_settings[$setting])) {
+			return null;
+		}
 		return $nagios_settings[$setting];
 	}