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', 'k2t6gnbnu7dgmdgbi8g0lke2m5', '216.73.216.121', '1761837406', '1761837406', '/shop_content.php?XTCsid=e65207aee44f142683bacdd3544c84a8&coID=2')

[XT SQL Error]