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', 'a9981c58f6cn1h5a8o8csdtnn2', '216.73.216.190', '1789543227', '1789543227', '/index.php?XTCsid=999cd663a216d89c548d84771c9fabe5')

[XT SQL Error]