collective.cover.widgets.textlinessortable: AttributeError: 'NoneType' object has no attribute 'absolute_url'

[zopyx]

c.c 1.6.5 + Plone 5.1RC 1 give me this error while editing a carousel tile.

  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.z3cform.inline_validation, line 33, in __call__
  Module z3c.form.group, line 98, in extractData
  Module z3c.form.form, line 148, in extractData
  Module z3c.form.field, line 301, in extract
  Module collective.cover.widgets.textlinessortable, line 155, in extract
AttributeError: 'NoneType' object has no attribute 'absolute_url'

[rodfersou]

@zopyx I can't reproduce this issue