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', '7v21psotln8l7m4p5j7jebbbp4', '216.73.216.102', '1793642443', '1793642443', '/xtshop/product_info.php?info=p498_.html')

[XT SQL Error]