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', 'mgto5b1dbgsji44r01tnqpdfb7', '216.73.217.120', '1793642011', '1793642011', '/index.php?XTCsid=9abd3adcd1f6be1347b53f20ac622098')

[XT SQL Error]