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', '4kldpgu2210i0sa9ufuhb17qv3', '216.73.216.245', '1752312597', '1752312597', '/xtshop/index.php?cat=c43_.html')

[XT SQL Error]