Nova tool, Computed property doesn't updated after Vuex mutation

Hi guys,

Can't figure out how to make computed property work with Vuex. Nova.liveStore.state gets updated after mutation, but cumputed (edit: lol) doesn't and returns initial empty object.

Can someone help with this, please?

// tool.js

import Vue from 'vue';
import Vuex from 'vuex';

Vue.use(Vuex);

Nova.booting((Vue, router) => {

    router.addRoutes([
        {
            name: 'my-tool',
            path: '/my-tool',
            component: require('./components/Tool'),
        },
    ])

    Nova.liveStore = new Vuex.Store({
        state: {
           items:{}, 
        },
        actions: {
            GET_ITEMS(context}) {
                Nova.request().get('/api/items').then(response => {
                    context.commit('SET_ITEMS', response.data)
                });
            },
        },
        mutations: {
            SET_ITEMS(state, items){
                Nova.liveStore._vm.$set(state, 'items', [...items])
            }
        },
    });
});

// Tool.vue

<template>
    <div>
        <div v-if="items">
            <select>
                <option value="null" disabled>Choose...</option>
                <option v-for="item in items" :value="item.id">{{ item.title }}</option>
            </select>
        </div>
    </div>
</template>

<script>
export default {
    computed: {
        items(){
            return Nova.liveStore.state.items;
        }
    },
    created() {    
        Nova.liveStore.dispatch('GET_ITEMS')
    },
}
</script>