application: Restore --new-window functionality

In case of no further arguments, open home folder. Commit
4e192481 "application: minimal port to handle_local_options()"
removed this, presumably accidentally. It makes clicking the "Files"
from favorites do nothing if Nautilus is already running (and it
always is running in classic mode as it handles desktop).

https://bugzilla.gnome.org/show_bug.cgi?id=738280