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', 'si9eci877fau6c1t0n7ov1ho82', '216.73.216.0', '1773456120', '1773456120', '/xtshop/product_info.php?info=p372_.html')

[XT SQL Error]