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', 'ldh326n851dq1rohr2v0j334u2', '216.73.216.123', '1789502715', '1789502715', '/index.php?XTCsid=67a1ee4a966bad4e2954e4e321814afb&cat=c12_Music.html')

[XT SQL Error]