how to use logic:Empty within c:forEach

[PC Leung]

The following coding always return blank values.
If I remove logic tags, it shows values correctly.
How can I use logic:Empty inside c:forEach ?

Thanks

<c:forEach items="${resultSet.rows}" var="row">
<tr>
<td width="20%">
<logic:empty name="${row.usernm}">
&nbsp
</logic:empty>
<logic:notEmpty name="${row.usernm}">
${row.usernm}
</logic:notEmpty>
</td>
<td width="50">
<logic:empty name="${row.usergrp}">
&nbsp
</logic:empty>
<logic:notEmpty name="${row.usergrp}">
${row.usergrp}
</logic:notEmpty>
</td>
</tr>
</c:forEach>