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', 'j7fugockh17lvksqj6032q7nl2', '216.73.216.9', '1758003476', '1758003476', '/popup_content.php?XTCsid=6c2468ca28c6c182aaed37353d32ae32&coID=1')

[XT SQL Error]