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', '2is7fgnn28ijt9aoseejld1ov3', '216.73.216.9', '1758094945', '1758094945', '/index.php?XTCsid=ec445a26a1be1b54e711876da9fff244&cat=c6_Lebensmittel.html')

[XT SQL Error]