code: @Nullable
    public static PasswordSalt createFromStringMaybe (@Nullable final String sSalt)
    {
      if (StringHelper.hasNoText (sSalt))
        return null;
  
      // Decode String to bytes
      // Throws an IllegalArgumentException if an invalid character is encountered
      final byte [] aBytes = StringHelper.getHexDecoded (sSalt);
      return new PasswordSalt (aBytes);
    }
docs: Try to create a {@link PasswordSalt} object from the passed string. First
  the string is hex decoded into a byte array and this is the password salt.
  
  @param sSalt
  The string to be used. May be <code>null</code>.
  @return <code>null</code> if the passed salt string is <code>null</code> or
  empty.
  @throws IllegalArgumentException
  if the passed salt string cannot be hex decoded.