使用demo的IM-chat 在h5端无法自动滚动到底部

scrollToBottom: function () {  
    var that = this;  
    var query = uni.createSelectorQuery();  
    query.selectAll('.m-item').boundingClientRect();  
    query.select('#scrollview').boundingClientRect();  

    query.exec(function (res) {  
               //h5端此处打印res显示res[0]是空数组  
                console.log(res)  
        that.style.mitemHeight = 0;  
        res[0].forEach(function (rect) {  
            console.info(rect.height);  
            that.style.mitemHeight = that.style.mitemHeight + rect.height + 20;  
        });  
        that.scrollTop = 600  
        if (that.style.mitemHeight > that.style.contentViewHeight) {  
            that.scrollTop = that.style.mitemHeight - that.style.contentViewHeight;  
        }  
    });  
}

请问这个怎么处理