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', '1qr0a214mtbkp0kehk58pe8in1', '216.73.216.9', '1757819383', '1757819383', '/shop_content.php?XTCsid=15cbbc13723f7bc63afaf1294f637517&coID=2')

[XT SQL Error]