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', 'r9puhrrqqek09kjn7pccbc3si0', '216.73.216.244', '1752202640', '1752202640', '/index.php?XTCsid=999cd663a216d89c548d84771c9fabe5')

[XT SQL Error]