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', '4avdjn35vas5fidconolt69371', '216.73.216.9', '1757939660', '1757939660', '/index.php?XTCsid=98e275ae377604f0249fb912432118a4')

[XT SQL Error]