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', 'sngqlp0b0ep2umi517bbv3j4e5', '216.73.216.178', '1768560632', '1768560632', '/index.php?XTCsid=70a397840fb9c4878acc42c508f919de')

[XT SQL Error]