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', '1h3lho3jamgn1bma15jvl7o5h4', '216.73.217.178', '1781736913', '1781736913', '/index.php?XTCsid=a63f52844b6e675f480eaf86612536c2&cat=c6_Foodstuffs.html')

[XT SQL Error]