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', '4jt0seqq5vuft0oo23kt966o84', '216.73.216.9', '1758110899', '1758110899', '/index.php?XTCsid=09c43bdddaf5303190cc96d38e6bc538')

[XT SQL Error]