Fixes missing require_once in parallel_model, a=chris

diff --git a/models/parallel_model.php b/models/parallel_model.php
index f4f526236..919ae6de7 100755
--- a/models/parallel_model.php
+++ b/models/parallel_model.php
@@ -44,6 +44,8 @@ require_once BASE_DIR."/lib/crawl_constants.php";
  * IndexManager so load the definition of this class
  */
 require_once BASE_DIR."/lib/index_manager.php";
+/** lookupSummaryOffsets uses word iterator*/
+require_once BASE_DIR.'/lib/index_bundle_iterators/word_iterator.php';
 /** For crawlHash function */
 require_once BASE_DIR."/lib/utility.php";
 /**