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', 'm4q61btv9hvdk883udm1m8bim3', '3.16.154.37', '1746767226', '1746767226', '/xtshop/index.php?cat=c48_.html')

[XT SQL Error]