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', '426b2ce4f4994e64a47192fee06556f3', '216.73.216.132', '1759460372', '1759460372', '/shop/product_info.php?XTCsid=041c8fc0413f2441df67fe52a6815a15&info=p108_.html')

[XT SQL Error]