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', '13ir77du1r86plsq98o2udg0n5', '216.73.216.244', '1752211686', '1752211686', '/product_info.php?language=de&info=p11_Fan-for-decorations.html&XTCsid=c63b24e231384cad64f954428cedcfc2')

[XT SQL Error]