Fix a MarkerRef call to get the active bookmark in Mercurial

Summary: See PHI1805. This call is constructed improperly and can lead to a fatal in `arc patch` under Mercurial.

Test Plan: In Mercurial, ran a valid `arc patch` operation.

Differential Revision: https://secure.phabricator.com/D21391

src/repository/api/ArcanistMercurialAPI.php

@@ -890,7 +890,10 @@ final class ArcanistMercurialAPI extends ArcanistRepositoryAPI {
 
   public function getActiveBookmark() {
     $bookmark = $this->newMarkerRefQuery()
-      ->withMarkerTypes(ArcanistMarkerRef::TYPE_BOOKMARK)
+      ->withMarkerTypes(
+        array(
+          ArcanistMarkerRef::TYPE_BOOKMARK,
+        ))
       ->withIsActive(true)
       ->executeOne();