public final static String ALLOW_EMPTY_PASSWORDS = "allowEmptyPasswords";// which is set to false by default.
....
allowEmptyPasswords = Boolean.parseBoolean((String) options.get(ALLOW_EMPTY_PASSWORDS));
....

if ((!"none".equals(this.authentication)) && (!this.allowEmptyPasswords) && ((tmpPassword == null) || (tmpPassword.length == 0)))
    {
      throw new LoginException("Empty passwords not allowed");
    }