get error adding gallery to portlet

[rileydog]

in portlet panel, add Plone true gallery portlet and get a pop up "modal error".
this is the associated error text:

Traceback (innermost last):
Module ZPublisher.Publish, line 138, in publish
Module ZPublisher.mapply, line 77, in mapply
Module ZPublisher.Publish, line 48, in call_object
Module plone.app.portlets.browser.formhelper, line 60, in call
Module z3c.form.form, line 233, in call
Module plone.z3cform.fieldsets.extensible, line 58, in update
Module plone.autoform.form, line 33, in updateFields
Module plone.autoform.base, line 54, in updateFieldsFromSchemata
Module plone.autoform.form, line 22, in schema
NotImplementedError: The class deriving from AutoExtensibleForm must have a 'schema' property

Plone 5.0.7 (5017)
CMF 2.2.10
Zope 2.13.26
Python 2.7.5 (default, Nov 6 2016, 00:28:07) [GCC 4.8.5 20150623 (Red Hat 4.8.5-11)]
PIL 3.4.2 (Pillow)