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', '6dj7psu7jpn9anj0cek34j5h26', '216.73.216.249', '1751519796', '1751519796', '/xtshop/product_info.php?info=p959_.html')

[XT SQL Error]