Vuejs doesn't show icon in component - vue.js

Question

I try to use Vuejs with jquery. I don't why this is not working. When first loading, icons doesn't seem. I don't know what is wrong. when you click on items, plus and minus icons seen and it is working as expected. But why it is not working in first loading ?
Any help will be appreciated.
var data = {
name: 'My Tree',
children: [{
name: 'hello'
}, {
name: 'wat'
}, {
name: 'child folder',
children: [{
name: 'child folder',
children: [{
name: 'hello'
}, {
name: 'wat'
}]
}, {
name: 'hello'
}, {
name: 'wat'
}, {
name: 'child folder',
children: [{
name: 'hello'
}, {
name: 'wat'
}]
}]
}]
}
// define the item component
Vue.component('item', {
template: '#item-template',
props: {
model: Object
},
computed: {
isFolder: function() {
return this.model.children &&
this.model.children.length
}
},
});
// boot up the demo
var demo = new Vue({
el: '#demo',
ready: function() {
},
data: {
treeData: data
}
});
Vue.nextTick(function() {
$('.tree li:has(ul)').addClass('parent_li').find(' > span').attr('title', 'Collapse this branch');
$('.tree li.parent_li > span').on('click', function(e) {
var children = $(this).parent('li.parent_li').find(' > ul > li');
if (children.is(":visible")) {
children.hide('fast');
$(this).attr('title', 'Expand this branch').find(' > i').addClass('icon-plus-sign').removeClass('icon-minus-sign');
} else {
children.show('fast');
$(this).attr('title', 'Collapse this branch').find(' > i').addClass('icon-minus-sign').removeClass('icon-plus-sign');
}
e.stopPropagation();
});
})
.tree {
min-height: 20px;
padding: 19px;
margin-bottom: 20px;
background-color: #fbfbfb;
border: 1px solid #999;
-webkit-border-radius: 4px;
-moz-border-radius: 4px;
border-radius: 4px;
-webkit-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.05);
-moz-box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.05);
box-shadow: inset 0 1px 1px rgba(0, 0, 0, 0.05)
}
.tree li {
list-style-type: none;
margin: 0;
padding: 10px 5px 0 5px;
position: relative
}
.tree li::before,
.tree li::after {
content: '';
left: -20px;
position: absolute;
right: auto
}
.tree li::before {
border-left: 1px solid #999;
bottom: 50px;
height: 100%;
top: 0;
width: 1px
}
.tree li::after {
border-top: 1px solid #999;
height: 20px;
top: 25px;
width: 25px
}
.tree li span {
-moz-border-radius: 5px;
-webkit-border-radius: 5px;
border: 1px solid #999;
border-radius: 5px;
display: inline-block;
padding: 3px 8px;
text-decoration: none
}
.tree li.parent_li>span {
cursor: pointer
}
.tree>ul>li::before,
.tree>ul>li::after {
border: 0
}
.tree li:last-child::before {
height: 30px
}
.tree li.parent_li>span:hover,
.tree li.parent_li>span:hover+ul li span {
background: #eee;
border: 1px solid #94a0b4;
color: #000
}
<link href="https://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.1/css/bootstrap-combined.min.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/1.0.26/vue.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet"/>
<ul id="demo">
<div class="tree well">
<item :model="treeData"></item>
</div>
</ul>
<script type="text/x-template" id="item-template">
<li>
<span><i v-if="isFolder" class="icon-minus-sign"></i> {{model.name}}</span>
<ul v-if="isFolder">
<item v-for="model in model.children" :model="model"></item>
</ul>
</li>
</script>

Answer 1

Actually it was my fault. I called wrong class name for the icon. I am updating and everything will work fine. I hope this vue recursive tree model will be useful for others.