Index: branches/version-2_12-dev/data/class/SC_Customer.php
===================================================================
--- branches/version-2_12-dev/data/class/SC_Customer.php	(revision 21867)
+++ branches/version-2_12-dev/data/class/SC_Customer.php	(revision 21968)
@@ -210,4 +210,7 @@
     // ログアウト　$_SESSION['customer']を解放し、ログに書き込む
     function EndSession() {
+        // セッション情報破棄の前にcustomer_idを保存
+        $customer_id = $_SESSION['customer']['customer_id'];
+
         // $_SESSION['customer']の解放
         unset($_SESSION['customer']);
@@ -218,6 +221,9 @@
         $objSiteSess = new SC_SiteSession_Ex();
         $objSiteSess->unsetUniqId();
+
         // ログに記録する
-        GC_Utils_Ex::gfPrintLog('logout : user='.$this->customer_data['customer_id'] ."\t".'ip='. $this->getRemoteHost(), CUSTOMER_LOG_REALFILE, false);
+        $log = sprintf("logout : user=%d\tip=%s",
+            $customer_id, $this->getRemoteHost());
+        GC_Utils_Ex::gfPrintLog($log, CUSTOMER_LOG_REALFILE, false);
     }