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', '7192rot8nq6vdpvf7f07qccdb5', '216.73.216.9', '1758157784', '1758157784', '/product_info.php?XTCsid=ec445a26a1be1b54e711876da9fff244&info=p15_25-balloons.html&language=de')

[XT SQL Error]