Ignore frames without names, becuase the code does not handle
them well. It does not affect those use case for which the
deduplication code was added.

Reviewed-on: https://gerrit.libreoffice.org/40222Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Tamás Zolnai <tamas.zolnai@collabora.com>
(cherry picked from commit 615c2a2c)

Change-Id: I08ad062b8b11cc06323467329d8c4e97bc4932dd
Reviewed-on: https://gerrit.libreoffice.org/40236Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
(cherry picked from commit de5afba4)