1366 - Incorrect integer value: '' for column 'customer_id' at row 1

insert into whos_online (customer_id, full_name, session_id, ip_address, time_entry, time_last_click, last_page_url) values ('', 'Guest', 'setbkhrbk9pnvm074djjrjroh5', '216.73.216.9', '1757821182', '1757821182', '/index.php?XTCsid=705a3b68bece48fd9b67e5e30d623e8e&cat=c13_Accessoires.html&language=de')

[XT SQL Error]