500 error using Mailchimp action

In PHP 8.1, if I use the Mailchimp action, and submit a form with a group of checkboxes, the is_email() check fails when $value is an array of checkboxes values.

html-forms/src/actions/class-mailchimp.php:80

// find email field
foreach ( $submission->data as $field => $value ) {
	if ( is_email( $value ) ) {
		$email_address = $value;
	}
}

Using is_string() function as part of the check should fix it:

// find email field
foreach ( $submission->data as $field => $value ) {
	if ( is_string( $value ) && is_email( $value ) ) {
		$email_address = $value;
	}
}