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', 'krci2g5i527bvu590sl6eob624', '216.73.216.9', '1757772832', '1757772832', '/index.php?XTCsid=18c3c05088c1e86a390dfdd4d4986991')

[XT SQL Error]