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', '2mk32l49kn36n1lm8pehoe5u73', '216.73.216.9', '1758156146', '1758156146', '/products_new.php?XTCsid=72205775904d1a5c41b590dd7b5ff1d6&language=en')

[XT SQL Error]