Updated obsolete class name.

module/VuFind/src/VuFind/Controller/AbstractSearch.php

@@ -209,7 +209,7 @@ class AbstractSearch extends AbstractBase
                 // We need to create and process an "empty results" object to
                 // ensure that recommendation modules and templates behave
                 // properly when displaying the error message.
-                $view->results = new VF_Search_Empty_Results($params);
+                $view->results = new \VuFind\Search\EmptySet\Results($params);
                 $view->results->performAndProcessSearch();
             } else {
                 // Unexpected error -- let's throw this up to the next level.