popover没有滚动条 求大佬们帮忙解答下 很急~

<a href="#picture" class="mui-btn mui-btn-primary mui-btn-block mui-btn-outlined" style="padding: 5px 20px;">打开actionsheet</a>
<div id="picture" class="mui-popover mui-popover-action mui-popover-bottom">
<div class="buttonalert">
<div class="title">我的优惠卷</div>
<div class="centent" id="centent">
<div class="my_youhuijuan">
<div class="yhj_left">
¥5000000
</div>
<div class="yhj_right1" >
满10000元可用
</div>
<div class="yhj_right2">
立即领取
</div>
<img src="img/red.png" >
</div>
</div>
</div>
<ul class="mui-table-view">
<li class="mui-table-view-cell">
<a href="#picture"><b>取消</b></a>
</li>
</ul>
</div>