Ticket #7551: fix_for_content_type_bug_improved.diff

django/contrib/contenttypes/generic.py

@@ -43 +43 @@
         Handles initializing an object with the generic FK instaed of
         content-type/object-id fields.
         """
-        if self.name in kwargs:
+        if self.name in kwargs and kwargs[self.name] != None:
             value = kwargs.pop(self.name)
             kwargs[self.ct_field] = self.get_content_type(obj=value)
             kwargs[self.fk_field] = value._get_pk_val()