Laravel 5.4 and Vue.js 2.0 Emitted value instead of an instance of Error

Question

I'm having hard time on this.

My specific error is on this code: If I'll try to remove it everything works but I need to display the data columns. I don't understand why it cause an error.

<select>
        <option v-for="column in columns">{{ column }}</option>
    </select>

My app.js

    import Vue from 'vue'
import DataViewer from './components/DataViewer.vue'

const app = new Vue({
    el: '#app',
    components: {

        DataViewer
    },
    data: {

    }

});

My DataViwer.vue

<template>
    <div class="dv">
    {{ title }}
    </div>
    <select>
        <option v-for="column in columns">{{ column }}</option>
    </select>

</template>

<script type="text/javascript">

    import Vue from 'vue'
    import axios from 'axios'
    export default {

        props: ['source', 'title'],
        data(){

            return {

                model: {},
                columns: {}
            }
        },
        created(){
            this.fetchIndexData()
        },
        methods: {

            fetchIndexData(){

                var vm = this
                axios.get(this.source)
                .then(function(response){

                    Vue.set(vm.$data, 'model', response.data.model)
                    Vue.set(vm.$data, 'columns', response.data.columns)

                    console.log(vm.$data.columns);
                })
                .catch(function(response){

                    console.log(response)
                })
            }
        }
    }

</script>

My ajax results:

Answer 1

I had the same warn and I found this decision: http://github.com.proxy.parle.co/ElemeFE/element/issues/4137

<el-tag v-for="tag in tags"> 
=> 
<el-tag v-for="(tag, index) in tags" :key="index">