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', 'p50bu2of4j723tn5t8tjqdvml7', '216.73.216.63', '1774159588', '1774159588', '/index.php?XTCsid=5480cf0b9118321f80660e645ab37ebb')

[XT SQL Error]