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', 'mru8bvdm93nej812dba74atii7', '216.73.216.141', '1751427509', '1751427509', '/shop_content.php?coID=2&XTCsid=6c2468ca28c6c182aaed37353d32ae32')

[XT SQL Error]