mui弹出菜单引入之后点击报错：Cannot read property 'offsetHeight' of null

mui弹出菜单引入之后点击报错：Cannot read property 'offsetHeight' of null
代码：

        <!-- 侧滑导航根容器 -->  
    <div class="mui-off-canvas-wrap mui-draggable mui-slide-in">  
      <!-- 菜单容器 -->  
      <aside class="mui-off-canvas-left">  
        <div class="">  
          <div class="mui-scroll mui-scroll-wrapper" id="offCanvasSideScroll">  
            <!-- 菜单具体展示内容 -->  
           <ul>  
             <li>1</li>  
             <li>1</li>  
             <li>1</li>  
             <li>1</li>  
             <li>1</li>  
           </ul>  
          </div>  
        </div>  
      </aside>  
      <!-- 主页面容器 -->  
      <div class="mui-inner-wrap mui-unactive">  
        <!-- 主页面标题 -->  
        <header class="mui-bar mui-bar-nav">  
          <a class="mui-icon mui-pull-left mui-icon-bars"></a>  
          <h1 class="mui-title">TEST</h1>  
          <!-- <a class="mui-icon mui-pull-right mui-icon-plus"></a> -->  
          <a href="#popover" id="openPopover" class="mui-icon mui-pull-right mui-icon-plus"></a>  
        </header>  
        <!-- 弹出菜单栏 -->  
        <div id="popover" class="mui-popover">  
            <ul class="mui-table-view mui-scroll-wrapper">  
                <li class="mui-table-view-cell"><a href="#">Item1</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item2</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item3</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item4</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item5</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item1</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item2</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item3</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item4</a></li>  
                <li class="mui-table-view-cell"><a href="#">Item5</a></li>  
            </ul>  
        </div>  
        <!-- 弹出菜单栏 -->  
        <div class="mui-content">  
          <div class="mui-scroll mui-scroll-wrapper" id="offCanvasContentScroll">  
            <!-- 主界面具体展示内容 -->  
            <ul>  
              <li>1</li>  
            </ul>  
          </div>  
        </div>  
        <nav class="mui-bar mui-bar-tab" id="nav">  
          <a id="tab_home" class="mui-tab-item mui-active" >  
            <span class="mui-icon mui-icon-home" ></span>  
            <span class="mui-tab-label">首页</span>  
          </a>  
          <a id="tab_message" class="mui-tab-item">  
            <span class="mui-icon mui-icon-email"></span>  
            <span class="mui-tab-label">消息</span>  
          </a>  
          <a id="tab_contact" class="mui-tab-item">  
            <span class="mui-icon mui-icon-contact"></span>  
            <span class="mui-tab-label">通讯录</span>  
          </a>  
          <a id="tab_setting" class="mui-tab-item" >  
            <span class="mui-icon mui-icon-gear"></span>  
            <span class="mui-tab-label">设置</span>  
          </a>  
        </nav>  
        <div class="mui-off-canvas-backdrop"></div>  
      </div>  
    </div>  

    <script src="./script/jquery-2.1.1.min.js" charset="utf-8"></script>  
    <script type="text/javascript" src="./script/api.js"></script>  
    <script src="./script/swiper-3.4.2.min.js" charset="utf-8"></script>  
    <script src="./script/mui.js" charset="utf-8"></script>  
    <script type="text/javascript">  
        apiready = function() {  

        };  
        // mui初始化  
        mui.init();  
        // 点击控制菜单滑动  
        $(".mui-icon-bars").on("tap",function(){  
          mui('.mui-off-canvas-wrap').offCanvas('show');  
        })  
        // 内容栏与菜单栏的内容都可以滚动显示  
        mui('#offCanvasSideScroll').scroll();      
        mui('#offCanvasContentScroll').scroll();  
        mui('#popover').scroll();  
    </script>

急！！！！！