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', 'gusi666j26sguouri34bk5g8j7', '216.73.216.147', '1751840560', '1751840560', '/products_new.php?XTCsid=0920dd1f7934388b33528580c92ca640')

[XT SQL Error]