In a civil matter, a person who has been convicted in a court of this Commonwealth of perjury, which term is hereby declared to include subornation of or solicitation to commit perjury, shall not be a competent witness for any purpose, although his sentence may have been fully complied with, unless the judgment of conviction be judicially set aside or reversed, or unless the matter is one to redress or prevent injury or violence attempted, done or threatened to his person or property, in which cases he shall be permitted to testify.