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', '2lddk8s9rf3u1kfof3agva7v73', '216.73.216.236', '1790263088', '1790263088', '/index.php?XTCsid=e867041440a0061f876d1c01655f4c12')

[XT SQL Error]