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', 'o28p2ad9u5ksb13nvub7slus11', '216.73.216.139', '1770296195', '1770296195', '/index.php?XTCsid=78ab7776912f9487a395d4474df042cd')

[XT SQL Error]