new-style dexterity profiles throw traceback on delete

[paregorios]

Observed on this new example: https://isaw.nyu.edu/people/staff/fee-fi-fo

Steps to re-create:

• Login to production with a user account that has admin permissions
• Navigate to /people/staff
• Select "add new" -> "profile" from the green tertiary menu bar
• On the add/edit profile form, enter a name, then scroll down to select the "save" button.
• Inspect the resulting user profile, which looks good
• From the green, tertiary menu bar, select "actions" -> "delete" and confirm deletion
• View a traceback like the following:

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 Products.CMFFormController.FSControllerPythonScript, line 105, in __call__
    Module Products.CMFFormController.Script, line 145, in __call__
    Module Products.CMFCore.FSPythonScript, line 127, in __call__
    Module Shared.DC.Scripts.Bindings, line 322, in __call__
    Module Shared.DC.Scripts.Bindings, line 359, in _bindAndExec
    Module Products.PythonScripts.PythonScript, line 344, in _exec
    Module script, line 6, in delete_confirmation
    <FSControllerPythonScript at /isaw/people/staff/fee-fi-fo/delete_confirmation>
    Line 6
    Module Products.CMFPlone.utils, line 655, in isLinked
    Module transaction._transaction, line 697, in rollback

InvalidSavepointRollbackError 

• Navigate to /people/staff and select the "contents" tab on the green, tertiary menu bar.
• Navigate to the last batch of content items
• Note that the profile in question has been deleted, despite the traceback

Desired remediation:

• Address the traceback, which will throw users into a tailspin (and which may indicate perhaps some problem with iterate integration or indexing or ???)