TYPO3 Core

tested on latest v8

what happened:

#1297759968: Exception while property mapping at property path "": No hmac found for property "options.templateRootPaths.0" (form element "myTestingForm" / "finishers.EmailToReceiver") #1528591585 (More information)

how to reproduce:

- create a form config with the Wizard in BE
- add a finisher 'Email to Receiver'
- go to edit the file itself (via IDE in my case)
- add a template override statement into the options section of the EmailToReceiver finisher

    options:
      templateRootPaths:
        100: 'EXT:styleguide/Resources/Private/Templates/'

- go back to the wizard (reload the frame)
- add another finisher
- safe the form config

=> results in the exception thrown.