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', '86esj032f876n4q37eftbc7pt1', '216.73.216.165', '1752392334', '1752392334', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=4299a8bbf7f56cb5a06703b866244eb3')

[XT SQL Error]