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', 'gk9t3qdmknuqv5a57c78rmmrh4', '216.73.216.180', '1767055821', '1767055821', '/product_info.php?XTCsid=80c3e9fc87b53cb0d288d19ef4e9b63c&info=p8_100-Placemats.html')

[XT SQL Error]