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', 'v9n4gkeos9933jnn845p0vna91', '216.73.217.172', '1790350119', '1790350119', '/shop_content.php?XTCsid=2f0d32e80e0e3a7e9efdd2dc2a571c8d&coID=3')

[XT SQL Error]