Fixed by this commit, closing.

 commit 3a48ce43d37e6d7e14a51ddfc8ead9c67a1bec41
 Author: Eli Zaretskii <eliz@gnu.org>
 Date:   2019-09-28 10:25:08 +0300

     Fix running on MS-Windows with non-existing home directory

     * lisp/startup.el (startup--xdg-or-homedot): Don't access a
     non-existent user home directory on windows-nt systems.
     (Bug#37536)