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', 'e1ukit4n6nlsek5mok5g0ft2n1', '216.73.216.119', '1758021260', '1758021260', '/xtshop/product_info.php?info=p957_.html')

[XT SQL Error]