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', '31ol391n98nad2rut8b1m7l451', '216.73.216.99', '1761904257', '1761904257', '/product_info.php?XTCsid=a0c8d0b3d08cb472c84559a313755d47&info=p13_Deco-ball.html')

[XT SQL Error]