problem with org-map-entries and the doc for export hooks

["Victor A. Stoichita" <victor@svictor.net>]

Greetings all!

I’m trying to use the example given here in the manual for "Export
hooks": https://orgmode.org/manual/Advanced-Export-Configuration.html

--8<---------------cut here---------------start------------->8---
(defun my-headline-removal (backend)
  "Remove all headlines in the current buffer.
BACKEND is the export back-end being used, as a symbol."
  (org-map-entries
   (lambda () (delete-region (point) (line-beginning-position 2)))))

(add-hook 'org-export-before-parsing-hook #'my-headline-removal)
--8<---------------cut here---------------end--------------->8---

However the export process hangs indefinitely emacs after evaluating this.
I have to C-g to quit. 
The same happens with the newer org-export-before-parsing-functions
instead of org-export-before-parsing-hook.

Is there something else that needs to be updated for the example to work?

Regards,
Victor