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', 'dju5m1tjc80ubfrk7uh91982c1', '216.73.216.55', '1768457883', '1768457883', '/index.php?XTCsid=9f22c7236683770c5f11f06a23996181')

[XT SQL Error]