InstallShield 读注册表函数 RegDBGetKeyValueEx ()执行失败

注： rtn = RegDBGetKeyValueEx(szKey, szNumName, nvType, svNumValue, nvSize);  调用失败
如果这个函数的几个参数没有初始化的值，调用就会导致失败

function RegeditReadLicense()
    STRING szKey, szNumName, szNumValue, svNumValue;
    NUMBER nvType, nvSize;
    NUMBER rtn;
begin
    szKey = "Software\\simpleTrbo";
    rtn = RegDBSetDefaultRoot (HKEY_CURRENT_USER);

    szNumName = "authority";
    nvType = REGDB_STRING;
    svNumValue = "";
    nvSize = -;
    rtn = RegDBGetKeyValueEx(szKey, szNumName, nvType, svNumValue, nvSize);
    if( rtn <  ) then
        return FALSE;
    endif;
    if( nvType != REGDB_STRING) then
        return FALSE;
    endif;
    if( nvSize <=  ) then
        return FALSE;
    endif;

    g_RegeditContentsString = svNumValue;
    return TRUE;
end;