Revert conditional for $success

Author: dannyvankooten

includes/forms/class-form-listener.php

@@ -149,7 +149,7 @@ public function process_unsubscribe_form( MC4WP_Form $form ) {
 	 */
 	public function respond( MC4WP_Form $form ) {
 
-		$success = $form->has_errors();
+		$success = ! $form->has_errors();
 
 		if( $success ) {