setDefaultDirectory "broken"

Display the proposed filename even when the URL
specified for the file picker directory is invalid.

As the Win32 file picker sadly allows both paths and URLs
for directories, users try paths on other more
restrictive platforms, and since the file picker there
shows neither the directory nor the file, they wrongly
conclude both are broken.

Patch by: me

(cherry picked from commit 42d181e7)

Change-Id: I3f99937b667d7fe5198f6445ccd4d0e22d48c7c7
Reviewed-on: https://gerrit.libreoffice.org/28426Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>