bug#30931: 27.0.50; Crash in "Automatic GC"

["Michał Kondraciuk" <k.michal@zoho.com>]

I was able to reproduce crash in the same place in bare Emacs versions 
27.0.50, 25.3, 24.4 with the form below.

(progn
   (defun on-overlay-modification (&rest args)
     (push nil buffer-undo-list))

   (defun crash ()
     (save-restriction
       (narrow-to-region 1 1)

       (let (end)
         (insert " 123aaa")
         (narrow-to-region 2 3)

         (setq end (set-marker (make-marker) 3))
         (save-restriction
           (widen)
           (lisp-indent-line))

         (garbage-collect)

         (overlay-put (make-overlay end (1+ end))
                      'modification-hooks '(on-overlay-modification)))))

   (with-current-buffer "*scratch*"
     (let ((buffer-undo-list t))
       (while t
         (erase-buffer)
         (crash)))))