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', '8i6hppelu8395qh5fqbsdv4b22', '216.73.216.125', '1786792833', '1786792833', '/products_new.php?XTCsid=15cbbc13723f7bc63afaf1294f637517&language=de')

[XT SQL Error]