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', 'ie51nu7j25jjg86p7nnhpv3p23', '216.73.216.130', '1760763220', '1760763220', '/index.php?XTCsid=32bc53310efafffaa756fafd3e8b8712')

[XT SQL Error]