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', 'l5kr5911bptu5mcuvq6nii9pj5', '216.73.216.197', '1751515050', '1751515050', '/product_info.php?language=de&info=p2_Bavarian-Pennant-Chain.html&XTCsid=07630e5b15e9155d8246af3ee660ca0e')

[XT SQL Error]