bug#44182: Bug in nftw function

Hello,

If I run nftw/ftw function over root directory ("/") it doesn't find any
file.

Example: (nftw "/" (lambda* (file #:rest args) (write file) #t))

Explanation from irc:
> [20:11]        <RhodiumToad> bug in nftw, or more precisely in one of the
> 			     functions it calls
> [20:12]        <RhodiumToad> (lambda () (go (clean filename) 0 0))  ;; but
> 			     (clean "/") returns "", which is clearly wrong
> [20:13]        <RhodiumToad> (clean) is removing any excess trailing /, but it
> 			     doesn't have the required special case for
> 			     filenames that are just "/" and nothing
> 			     else

--
Best Regards,
Matija Obid