Improve fix of PR #321

checking hasattr(self, 'fieldsets') alway returns true, and produces
different effects. The hasattr(self, 'declared_fieldsets') was designed
to detect whether Django injected that attribute.

Amends: 5e150ea

polymorphic/admin/childadmin.py

@@ -183,7 +183,7 @@ def history_view(self, request, object_id, extra_context=None):
 
     def get_fieldsets(self, request, obj=None):
         # If subclass declares fieldsets or fields, this is respected
-        if hasattr(self, 'fieldsets') or hasattr(self, 'fields') or not self.base_fieldsets:
+        if self.fieldsets or self.fields or not self.base_fieldsets:
             return super(PolymorphicChildModelAdmin, self).get_fieldsets(request, obj)
 
         # Have a reasonable default fieldsets,