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', 'nv6cuf6j0eupbdbes15v95jtc6', '216.73.216.60', '1760502473', '1760502473', '/index.php?XTCsid=c4868caa6063e92eced2da36e17c7aa0')

[XT SQL Error]