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', 'c9l028gsrnvjt92svr75dvcqr2', '216.73.216.80', '1751326574', '1751326574', '/index.php?cat=c2_Decoration.html&XTCsid=a48c8beab5e62c5a2ab061d7d44cf227')

[XT SQL Error]