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', '9nhhm2v7s6evi8dk5k0hi4bb86', '216.73.216.60', '1760609832', '1760609832', '/index.php?XTCsid=bb255b32dcfa95d840686d21071f0a9f')

[XT SQL Error]