From fc460b775e966d294776120baafa36d94ce99f19 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wilson=20J=C3=BAnior?= <wilsonpjunior@gmail.com>
Date: Fri, 2 Dec 2011 09:46:51 -0200
Subject: [PATCH] Small improvements for item_frequencies

---
 mongoengine/queryset.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mongoengine/queryset.py b/mongoengine/queryset.py
index 90547e22..0da17180 100644
--- a/mongoengine/queryset.py
+++ b/mongoengine/queryset.py
@@ -1572,8 +1572,10 @@ class QuerySet(object):
                     field.forEach(function(item) {
                         emit(item, 1);
                     });
-                } else {
+                } else if (field) {
                     emit(field, 1);
+                } else {
+                    emit(null, 1);
                 }
             }
         """ % dict(field=field)