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', 'kb4gv5kn1rafc3pod85ot444d4', '216.73.216.94', '1751736208', '1751736208', '/xtshop/shop_content.php?coID=2')

[XT SQL Error]