Traceback (innermost last):
  Module ZPublisher.Publish, line 115, in publish
  Module ZPublisher.mapply, line 88, in mapply
  Module ZPublisher.Publish, line 41, in call_object
  Module zope.formlib.form, line 757, in __call__
  Module Products.Five.formlib.formbase, line 54, in update
  Module zope.formlib.form, line 720, in update
  Module plone.fieldsets.form, line 30, in setUpWidgets
  Module zope.formlib.form, line 385, in setUpEditWidgets
  Module zope.schema._bootstrapfields, line 171, in get
  Module opencore.redirect.management, line 83, in fget
AttributeError: 'NoneType' object has no attribute 'url'