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', '8g997k35s4al51mg29bc60p221', '216.73.216.185', '1752883149', '1752883149', '/products_new.php?XTCsid=adfc0e11230ba3fd4e1b3e35346ba1dc')

[XT SQL Error]