finetune the get_queryset() call from PR django-polymorphic#20

Author: vdboor

polymorphic_tree/managers.py

@@ -29,8 +29,10 @@ def toplevel(self):
  """
  Return all nodes which have no parent.
  """
- try:
- return self.get_queryset().toplevel()
- except:
- pass
- return self.get_query_set().toplevel()
+ if hasattr(PolymorphicManager, 'get_queryset'):
+ # Latest django-polymorphic for Django 1.7
+ qs = self.get_queryset()
+ else:
+ qs = self.get_query_set()
+
+ return qs.toplevel()