Facebook logout

I have added Facebook_Auth to a site. I can log in ok using Facebook ok from the site but when I log out I get

Fatal error: Uncaught exception 'FacebookRestClientException' with message 'A session key is required for calling this method' in /home/topifa/public_html/sites/all/modules/facebook_auth/facebook-platform/php/facebookapi_php5_restlib.php:2457 Stack trace: #0 /home/topifa/public_html/sites/all/modules/facebook_auth/facebook-platform/php/facebookapi_php5_restlib.php(302): FacebookRestClient->call_method('facebook.auth.e...', Array) #1 /home/topifa/public_html/sites/all/modules/facebook_auth/facebook-platform/php/facebook.php(218): FacebookRestClient->auth_expireSession() #2 /home/topifa/public_html/sites/all/modules/facebook_auth/facebook_auth.module(156): Facebook->expire_session() #3 /home/topifa/public_html/includes/module.inc(471): facebook_auth_user('logout', NULL, Object(stdClass)) #4 /home/topifa/public_html/modules/user/user.pages.inc(151): module_invoke_all() #5 /home/topifa/public_html/includes/menu.inc(348): user_logout('facebook_auth_u...', Array) #6 /home/topifa/public_html/index.php(18): menu_execute_active_ha in /home/topifa/public_html/sites/all/modules/facebook_auth/facebook-platform/php/facebookapi_php5_restlib.php on line 2457

Any ideas why please. It is the first time I have tried adding Facebook to Drupal

Thanks