Ticket #7551: fix_for_content_type_bug.diff

django/contrib/contenttypes/generic.py

@@ -41 +41 @@
         """
         if self.name in kwargs:
             value = kwargs.pop(self.name)
-            kwargs[self.ct_field] = self.get_content_type(obj=value)
-            kwargs[self.fk_field] = value._get_pk_val()
+            if value != None:
+                kwargs[self.ct_field] = self.get_content_type(obj=value)
+                kwargs[self.fk_field] = value._get_pk_val()
 
     def get_content_type(self, obj=None, id=None):
         # Convenience function using get_model avoids a circular import when