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', 'af65dd474d76de1ff00fb4a1bf8bf4ef', '216.73.216.213', '1767295127', '1767295127', '/shop/product_info.php?info=p156_.html')

[XT SQL Error]