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', 'be2lpvee2s04sp3e6gd2uld1p6', '216.73.216.9', '1758183336', '1758183336', '/index.php?XTCsid=54fe90272f17578d553875e28583f966')

[XT SQL Error]