Help setting nadvice for indent-region

[Kaushal Modi <kaushal.modi@gmail.com>]

Hi,

I'd like to advice indent-region so that if a region is not select, it
indents between (point-min) and (point-max).

So I have this:

=====

(defun adv/indent-region (args)
  (when (not mark-active)
    (setq args (list (point-min) (point-max))))
  args)
(advice-add 'indent-region :filter-args #'adv/indent-region)

=====

This usually works, unless I have just launched a fresh buffer in which
there is no mark set.

If I do M-: (mark) in that buffer, I get nil.
In that case, if I call M-x indent-region (with no region selected), I get
this error backtrace:

Debugger entered--Lisp error: (error "The mark is not set now, so there is
no region")
  call-interactively(indent-region nil nil)
  command-execute(indent-region)

If it looks like the error is triggered by call-interactively even before
the advice gets to do its thing.

How can I resolve this using nadvice?

Thanks.

Kaushal Modi