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', '6287cfe3930a248d8d002efd49eb33af', '216.73.216.213', '1767340708', '1767340708', '/shop/product_info.php?info=p139_.html')

[XT SQL Error]