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', 'es57337iedmpd5ugfi5p0gerl2', '216.73.216.147', '1751964363', '1751964363', '/index.php?XTCsid=5480cf0b9118321f80660e645ab37ebb')

[XT SQL Error]