Regression test: creating a document type full of compounds causes an error

Steps to reproduce:

1. Go to the content editor, switch to "DocumentTypes".
2. Create a new document type.
3. Add all available compound fields.
4. Hit "Save" and "Done". The error will occur.
5. The same error will occur even if you leave the content editor, refresh the website and get back to it and hit "Edit". So this becomes non-editable.

No error shows in hap config or browser console. Error image attached.