Zend_Search_Lucene: fix for sorting result by multiple fields.

git-svn-id: http://framework.zend.com/svn/framework/standard/trunk@18601 44c647ce-9c0f-0410-b52a-842ac1e357ba

library/Zend/Search/Lucene.php

@@ -987,6 +987,7 @@ class Zend_Search_Lucene implements Zend_Search_Lucene_Interface
                 }
 
                 $sortArgs[] = &$valuesArray;
+                unset($valuesArray);
 
                 if ($count + 1 < count($argList)  &&  is_integer($argList[$count+1])) {
                     $count++;