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', '94aa9125b449db27586bc042a439857d', '216.73.216.169', '1755543162', '1755543162', '/shop/index.php?cat=c25_.html')

[XT SQL Error]