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', '7i387st2kmrqtkgkvmppv3to46', '54.146.41.3', '1493061186', '1493061186', '/shop/304SP2.1_release/xtcommerce/index.php')

[XT SQL Error]