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', '9loolabn1mebd3p02rd9tfd363', '216.73.216.140', '1763557914', '1763557914', '/index.php?XTCsid=0b86e5b33fa3387ebc47b5f03d369409')

[XT SQL Error]