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', 'pr58n0m4ks9ndpfdq6m1g23kq1', '216.73.217.103', '1779160770', '1779160770', '/index.php?XTCsid=999cd663a216d89c548d84771c9fabe5')

[XT SQL Error]