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', 'b735h78khtbsnn1tasq54kvku2', '216.73.216.7', '1758227124', '1758227124', '/shop_content.php?XTCsid=0c2bbf6d25a69215077c72e03a0d4646&coID=1')

[XT SQL Error]