dedecms判断二级栏目为空不显示

{dede:channelartlist typeid='top'}
<li><a href="{dede:field name='typeurl'/}">{dede:field name='typename'/}</a>
{dede:php}
$id = $refObj->Fields['id'];
$sql = ("SELECT * FROM dede_arctype where reid ='$id'");
$db->SetQuery($sql);
$db->Execute();
if($db->GetTotalRow()){
echo '<ul>';
while($row = $db->GetArray()){
$url = str_replace('{cmspath}','',($row[typedir]));
echo "<li><a href=".$url.">".($row[typename])."</a></li>";
};
echo '</ul>';
};
{/dede:php}
</li>
{/dede:channelartlist}