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', '2hks38a45nqv8j5g4cja5gcqm7', '216.73.216.9', '1757991386', '1757991386', '/index.php?XTCsid=d0fb6f95a363340d124d7dc76e615e44&cat=c13_Accessoires.html&language=de')

[XT SQL Error]