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', 'tiavulo6l8bi51kihh42s6so36', '216.73.216.165', '1752392807', '1752392807', '/product_info.php?info=p2_Bavarian-Pennant-Chain.html&XTCsid=e65207aee44f142683bacdd3544c84a8')

[XT SQL Error]