rhbz#1080196: Delete the destination first then paste.

Deleting in-between pasting was causing the block iterators to become
invalid when the deletion took place, which resulted in a segfault.

Also cleaned up the bits about handling filtered rows.  It was using the
old row flag which is empty these days (so it never would have worked).
Plus we do bail out earlier if the destination contains a filtered row.

Change-Id: I78d3ee8bce1647c1c8685f92a3df3c38cc014811
(cherry picked from commit 2ec45841b97a994ef9dca854e142598a063877fd)
Reviewed-on: https://gerrit.libreoffice.org/8786
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>