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', 'hbln4slkkaagdutq11f364it32', '216.73.216.110', '1752059753', '1752059753', '/shop_content.php?coID=4&XTCsid=4299a8bbf7f56cb5a06703b866244eb3')

[XT SQL Error]