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', '9k5ptnso6le4336ucdp7u0bop2', '216.73.216.80', '1751315365', '1751315365', '/index.php?XTCsid=8b7cba01600c404a966486e68846ce8d')

[XT SQL Error]