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', 'vmpnts22hvq17n6seb7an9au50', '216.73.216.165', '1752394261', '1752394261', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=38717c4dd62e88001622b2c7b8b8372a')

[XT SQL Error]