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', 'skcn0iohrdnkdpcdofcen52ho1', '216.73.216.197', '1751520638', '1751520638', '/index.php?language=en&cat=c5_Crockery.html&XTCsid=5452c15f57f0ea9ce022f9dc9cfaa045')

[XT SQL Error]