Merge pull request #391 from doctrine/2.1.x

Merge 2.1.x up into 2.2.x

src/ArrayCollection.php

@@ -480,7 +480,7 @@ public function matching(Criteria $criteria)
         $offset = $criteria->getFirstResult();
         $length = $criteria->getMaxResults();
 
-        if ($offset || $length) {
+        if ($offset !== null && $offset > 0 || $length !== null && $length > 0) {
             $filtered = array_slice($filtered, (int) $offset, $length, true);
         }