无选择对象，提交钮变灰

<s:if test="userList==null||userList.isEmpty()" >

   <s:if test="paginationSupport.items.size>0">
      &nbsp;
<input type="image" src="../../common/images/button/submit.gif" onclick="Common.clickSelectObject(Common.radioValue('operate'));return false" mouseover="true" border="0" /></td>
      </s:if>
      <s:else>
&nbsp;<input type="image" style="FILTER:gray()" //变灰  disabled="disabled"  //按钮禁用
src="../../common/images/button/submit.gif"  mouseover="true" border="0" />
      </s:else>