PHP Debug showing error with latest version

hi,

We are getting the following error with the latest version 8.1.4:

PHP Notice: Undefined index: tracking_actid in /opt/bitnami/apps/wordpress/htdocs/wp-content/plugins/activecampaign-subscription-forms/activecampaign.php on line 910

This is the snippet:

$data = array(
        "ac_settings" => array(
            "tracking_actid" => $settings["tracking_actid"],
            "site_tracking_default" => 1,
        ),
        "user_email" => $user_email,
    );

PHP 7.4
WP 5.6

What would be the solution to that?

Appreciate your help.