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', 'hi5s7bqt3iq97mv8qtu9ecmt74', '216.73.216.9', '1758132134', '1758132134', '/index.php?XTCsid=3fbd18868a5773472cbf49fb316cd42b')

[XT SQL Error]