bug#25992: perform-replace leaves mark-active when not transient-mark-mode

[Eli Zaretskii]

> Date:  Mon, 06 Mar 2017 09:06:56 -0800
> From:  Keith David Bershatsky <esq@lawlist.com>
> Cc:  25992@debbugs.gnu.org
> 
> In a custom test to determine whether the region is active, I had been 
> testing mark-active prior to using (region-beginning) and/or (region-end) to 
> avoid trowing an error "The mark is not set now, so there is no region".  
> When the following is true `(and mark-active (= (region-beginning) 
> (region-end)))`, my custom function should return nil.

Why can't you just check whether the function 'mark' returns nil?