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', '6kdfsbd27ojuetauuqv3e72m15', '216.73.216.9', '1758220219', '1758220219', '/popup_content.php?XTCsid=a63f52844b6e675f480eaf86612536c2&coID=1')

[XT SQL Error]