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', '5ufou1fqi1798pqo4hp1ql0506', '216.73.216.110', '1752051927', '1752051927', '/index.php?cat=c9_Tischdekoration.html&XTCsid=e786190734d0d1381d87ecc8370dc449')

[XT SQL Error]