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', 'vf1suu4s2kb4a82869p6rvj4b3', '216.73.216.244', '1752213154', '1752213154', '/product_info.php?language=en&info=p9_Paper-Lantern.html&XTCsid=4299a8bbf7f56cb5a06703b866244eb3')

[XT SQL Error]