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', '8ovovl8tq68t4807e1tt6ih1f1', '216.73.216.63', '1774341241', '1774341241', '/index.php?XTCsid=d09f2e4db7570f9ced41479f2d9c41e4')

[XT SQL Error]