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', 'druja1uo7ln14r63t22th2jcl2', '216.73.216.110', '1752054500', '1752054500', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=33509f1bee4ee2cbb673a74e5faae0d4')

[XT SQL Error]