Any register of deeds may continue to use the register index heretofore provided by law until space in such record is exhausted after which date the index provided for in §§ 7-9-11 and 7-9-12 shall be used; provided, that any such instrument is not to be deemed defectively filed by reason of any errors in copy filed which do not tend to mislead a party interested; and the negligence of an officer with whom any such instrument is filed does not prejudice the rights of the person for whose protection it is filed.
SDCL 7-9-13