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', 'vrqhpt8a5umlfjmhh9k4bimes6', '216.73.216.7', '1758226522', '1758226522', '/products_new.php?XTCsid=adfc0e11230ba3fd4e1b3e35346ba1dc')

[XT SQL Error]