Index: branches/feature-module-update/data/class/SC_CartSession.php
===================================================================
--- branches/feature-module-update/data/class/SC_CartSession.php	(revision 15532)
+++ branches/feature-module-update/data/class/SC_CartSession.php	(revision 16010)
@@ -244,5 +244,6 @@
     // 前頁のURLを取得する
     function getPrevURL() {
-        return $_SESSION[$this->key]['prev_url'];
+        return isset($_SESSION[$this->key]['prev_url'])
+            ? $_SESSION[$this->key]['prev_url'] : "";
     }