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', 'si21md8l8cq956cmb2e9itc583', '216.73.216.102', '1793564661', '1793564661', '/xtshop/product_info.php?info=p434_.html')

[XT SQL Error]