Error while saving a non-initialized JsonProperty

[eyalhei]

google-cloud-ndb==0.1.0

code example:

from google.cloud import ndb
with get_datastore_context():
    class Test(ndb.Model):
        prop = ndb.JsonProperty(compressed=True, json_type=dict)

    a = Test()
    a.put()

I get an exception:

Traceback (most recent call last):
    a.put()
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/_options.py", line 91, in wrapper
    return wrapped(*pass_args, _options=_options, **kwargs)
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 4917, in _put
    return self._put_async(_options=_options).result()
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 190, in result
    self.check_success()
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 137, in check_success
    raise self._exception
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/tasklets.py", line 293, in _advance_tasklet
    yielded = self.generator.send(send_value)
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 4974, in put
    ds_entity = _entity_to_ds_entity(self)
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 718, in _entity_to_ds_entity
    names = prop._to_datastore(entity, data)
  File "<venv>/lib/python3.7/site-packages/google/cloud/ndb/model.py", line 2482, in _to_datastore
    if not value.startswith(_ZLIB_COMPRESSION_MARKER):
AttributeError: 'NoneType' object has no attribute 'startswith'

Thanks for your awesome work!

[cguardia]

I created a PR for this. Should be merged in a couple of days. Thanks a lot for helping us find and fix these issues.

#200

[cguardia]

Fixed via #200.

[eyalhei]

Hi, I know you just released a version lately, but is there any chance this fix be released soon?