* lisp/simple.el (undo-redo): Default arg to 1 to avoid error when
called from Lisp without args (bug#51718).
Copyright-paperwork-exempt: yes
(let ((undo-in-progress t))
(while (and (consp ul) (eq (car ul) nil))
(setq ul (cdr ul)))
- (primitive-undo arg ul)))
+ (primitive-undo (or arg 1) ul)))
(new-pul (undo--last-change-was-undo-p new-ul)))
(message "Redo%s" (if undo-in-region " in region" ""))
(setq this-command 'undo)