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', '9vef625atr1jaki5rha93im0p3', '216.73.216.170', '1762026968', '1762026968', '/index.php?XTCsid=a1e615fe261b6ebee1d6d44580f7a3af')

[XT SQL Error]