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', 'n5stfcp6k3i4ne7m5um0v6dfg3', '216.73.217.147', '1777916738', '1777916738', '/shop_content.php?XTCsid=3547ee950f9337e348e5e07def1466f0&coID=2')

[XT SQL Error]