pbootcms文章列表没有缩略图时不显示默认图片的方法

{pboot:list scode={sort:scode}}
<a href="[list:link]" rel="external nofollow" title="[list:title]">
<div class="flex-column">
{pboot:if('[list:isico]'=='1')}
<img src="[list:ico]" alt="[list:title]">
{/pboot:if}
<div class="text-box">
<h4>[list:title]</h4>
<p class="intro hidden-sm">[list:content drophtml=1 dropblank=1 lencn=120]</p>
<p>
<span><i class="fa fa-clock-o" aria-hidden="true"></i> [list:date style=Y-m-d]</span>
<span><i class="fa fa-eye" aria-hidden="true"></i> [list:visits] 浏览</span>
<span><i class="fa fa-thumbs-up" aria-hidden="true"></i> [list:likes] 点赞</span>
</p>
</div>
</div>
</a>
{/pboot:list}

{pboot:if('[list:isico]'=='1')}
<img src="[list:ico]" alt="[list:title]">
{/pboot:if}