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', 'eih5j3556rjd4s0rgtto0s3k71', '216.73.216.99', '1761946966', '1761946966', '/product_info.php?XTCsid=33509f1bee4ee2cbb673a74e5faae0d4&info=p15_25-balloons.html')

[XT SQL Error]