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', 'frbh3evn02dhp17s03vmcl2d21', '216.73.216.9', '1757783099', '1757783099', '/shop_content.php?XTCsid=a61b1c7c4e21580bd9d4e85a32d692bc&coID=1')

[XT SQL Error]