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', '8rtev6nfdt7lk7n5u9uop9n884', '216.73.216.60', '1760502694', '1760502694', '/shop_content.php?XTCsid=3547ee950f9337e348e5e07def1466f0&coID=1')

[XT SQL Error]