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', '6v1hbei2sl1lu1v91ssbvubt61', '216.73.217.172', '1790518620', '1790518620', '/index.php?XTCsid=68d3e27ea16f220cd89842c811d00725')

[XT SQL Error]