如图所示，在某些手机型号的画面尺寸下，底部导航栏和页面底部之间会出现缝隙。请问该如何解决？
<nav class="mui-bar mui-bar-tab">
<a class="mui-tab-item">
<span class="mui-icon mui-icon-home"></span>
<span class="mui-tab-label">首页</span>
</a>
<a class="mui-tab-item">
<span class="mui-icon mui-icon mui-icon-list"></span>
<span class="mui-tab-label">商品列表</span>
</a>
<a class="mui-tab-item">
<span class="mui-icon mui-icon-extra mui-icon-extra-cart"></span>
<span class="mui-tab-label">购物车</span>
</a>
<a class="mui-tab-item mui-active">
<span class="mui-icon mui-icon mui-icon-person"></span>
<span class="mui-tab-label">我的</span>
</a>
</nav>
