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', 'l140e4spqbgspqmqjl6ekqqrb4', '216.73.216.80', '1751321651', '1751321651', '/index.php?cat=c4_Beer-Mugs.html&XTCsid=7c604026da355cfd6a094c68b431572d')

[XT SQL Error]