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', 'tke939ovm8ol7bjbcptsjl4if1', '216.73.216.180', '1766082291', '1766082291', '/index.php?XTCsid=cd27851dfbd887f886970c8f8e48fdfb')

[XT SQL Error]