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', '88q7il5891kiolujv5q5f18l91', '18.97.9.168', '1742455506', '1742455506', '/xtshop/product_info.php?info=p1004_.html')

[XT SQL Error]