Cosmetics for #2041

celery/result.py

@@ -718,7 +718,10 @@ class ResultSet(ResultBase):
 
     @property
     def supports_native_join(self):
-        return len(self.results) > 0 and self.results[0].supports_native_join
+        try:
+            return self.results[0].supports_native_join
+        except IndexError:
+            pass
 
     @property
     def backend(self):

celery/tests/tasks/test_result.py

@@ -278,7 +278,8 @@ class test_ResultSet(AppCase):
 
     def test_get_empty(self):
         x = self.app.ResultSet([])
-        x.join = Mock()
+        self.assertIsNone(x.supports_native_join)
+        x.join = Mock(name='join')
         x.get()
         self.assertTrue(x.join.called)