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', '6e8tf0cqbpf654l9s8ejg8uvt4', '216.73.216.9', '1758099006', '1758099006', '/shop_content.php?XTCsid=e65207aee44f142683bacdd3544c84a8&coID=2')

[XT SQL Error]