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', '7pj5g69b043fn1ckvioos3id66', '216.73.216.31', '1774958437', '1774958437', '/popup_content.php?XTCsid=ec445a26a1be1b54e711876da9fff244&coID=1')

[XT SQL Error]