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', 'ub8uktu9nb85sqk69vsqpt3k21', '18.97.9.172', '1750673441', '1750673441', '/xtshop/product_info.php?info=p1099_.html')

[XT SQL Error]