remove a small warning

pages/index.vue

@@ -38,7 +38,7 @@ export default {
       this.$fetch()
     }
   },
-  data ({ $store }) {
+  data () {
     return {
       mdiMagnify, mdiCloseCircle,
       isCurrentMonth: true,
@@ -89,6 +89,7 @@ export default {
   created () {
     this.$root.$on('dayclick', this.dayChange)
     this.$root.$on('monthchange', this.monthChange)
+    if (process.client) {
       this.storeUnsubscribe = this.$store.subscribeAction( { after: (action, state) => {
         if (action.type === 'setFilter') {
           if (this.filter.query && this.filter.query.length > 2) {
@@ -99,6 +100,7 @@ export default {
           }
         }
       }})
+    }
   },
   destroyed () {
     this.$root.$off('dayclick')