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', '4j3l52cmkfahp627hqh1udpfh2', '216.73.216.127', '1752882219', '1752882219', '/index.php?XTCsid=a3b8bf2959b629f4e700fd83d8e68631')

[XT SQL Error]