Any sale of revenue bonds or warrants of port districts heretofore made, whether at public or private sale and whether at par or less than par as authorized herein, and any terms, conditions, and covenants of any revenue bonds or warrants of port districts heretofore issued, are hereby declared to be valid, legal, and binding in all respects: PROVIDED, HOWEVER, That this section shall not be construed to exonerate any officer or agent of any such district from any liability for any acts which were committed fraudulently or in bad faith.