If history system is disabled, we should be using a null object - not…

… throw an exception

There is code in turba, for example, that will fatally error if history
system is not configured.  This is wrong; the information should simply
be empty.

framework/Core/lib/Horde/Core/Factory/History.php

@@ -61,12 +61,8 @@ public function create(Horde_Injector $injector)
         }
 
         if (is_null($history)) {
-            throw new Horde_Exception(
-                Horde_Core_Translation::t("The History system is disabled.")
-            );
-        }
-
-        if ($cache = $injector->getInstance('Horde_Cache')) {
+            $history = new Horde_History_Null();
+        } elseif ($cache = $injector->getInstance('Horde_Cache')) {
             $history->setCache($cache);
         }