Weird Error

[INFO    ] Executing state dockerng.image_present for localhost:5000/docker/sofootdb3:latest
[DEBUG   ] "GET /v1.24/images/json?only_ids=0&all=0 HTTP/1.1" 200 None
[ERROR   ] An exception occurred in this state: Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/salt/state.py", line 1624, in call
    **cdata['kwargs'])
  File "/usr/lib/python2.7/site-packages/salt/loader.py", line 1491, in wrapper
    return f(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/salt/states/dockerng.py", line 443, in image_present
    all_tags = __salt__['dockerng.list_tags']()
  File "/usr/lib/python2.7/site-packages/salt/modules/dockerng.py", line 2212, in list_tags
    for repo_tag in item['RepoTags']:
TypeError: 'NoneType' object is not iterable

And the part of the state which causes this ...

force a rebuild of the docker image from dockerfile generated at runtime

localhost:5000/docker/{{pillar ["app"] }}:latest:
dockerng.image_present:

• build: /data/docker/{{pillar ["app"] }}
• force: True