fdo#72774: Ensure that all the group fields are in cache upon file load.

This resolves the originally reported issue in that bug (in Comment 1).

Change-Id: I6fb85cff1eafb78d784605aa08e7d992a1ac36e0
(cherry picked from commit 256e4ccba8a331f2d30c6b5da9dca70206deadae)
Reviewed-on: https://gerrit.libreoffice.org/7302
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>