Getting TypeError on datastore put()

[Vivek Puri]

I am getting the following error when trying to make a put call(to
update an existing row). Would someone from Google team have an idea
as to why this might be happening.


'NoneType' object is not iterable
Traceback (most recent call last):
File "/base/data/home/apps/app_name/app_version/path/file_name.py",
line 46, in post
linkObj.put()
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 1014, in put
self._populate_internal_entity()
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 989, in _populate_internal_entity
self._entity = self._populate_entity(_entity_class=_entity_class)
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 1054, in _populate_entity
self._to_entity(entity)
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 963, in _to_entity
datastore_value = prop.get_value_for_datastore(self)
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 3360, in get_value_for_datastore
super(ListProperty, self).get_value_for_datastore(model_instance))
File "/base/python_runtime/python_lib/versions/1/google/appengine/
ext/db/__init__.py", line 3318, in validate_list_contents
for item in value:
TypeError: 'NoneType' object is not iterable

[Ikai Lan]

Do you have any more information about this? What is the type? Can you post code?