Admin app raises exception, if GFK referenced object has been deleted.

[h2he]

--- admin.py.orig   2015-03-04 13:39:24.040388839 +0200
+++ admin.py    2015-03-04 13:40:32.153011770 +0200
@@ -18,7 +18,11 @@
 class EmailConfirmationAdmin(admin.ModelAdmin):

     def show_content_type(self, obj):
-        return obj.content_object._meta.object_name
+        return (
+            obj.content_object._meta.object_name
+            if obj.content_object
+            else None
+        )