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', '9tb2sr7jhmmrdcjps02u83v6o6', '18.97.9.168', '1752891995', '1752891995', '/xtshop/product_info.php?info=p1098_.html')

[XT SQL Error]