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', '2m8ntea43ee1vlnp0v1n7f2u14', '216.73.216.127', '1752882221', '1752882221', '/index.php?XTCsid=3fd18fb8284d55117a0b70b0307b23de')

[XT SQL Error]