The word "owner," as used in this article, shall mean the owner of the freehold estate, as appears by the deed of record, and it shall not include reversioners, remaindermen, trustees, or mortgagees, who need not be notified by publication, or served by process, but shall be represented by the present owners of the freehold estate in any proceeding under this article: Provided, however, That all procedure under this article being in rem, failure to notify or summon into court any owner or other person shall in nowise invalidate any act, proceeding, order or decree, under this article or under any act or law invoked in aid thereof.