fix(powered-by): ensure search store is not required

Author: rayrutjes

src/components/PoweredBy.vue

@@ -23,6 +23,14 @@
 <script>import algoliaComponent from '../component';
 export default {
   mixins: [algoliaComponent],
+  props: {
+    searchStore: {
+      type: Object,
+      default() {
+        return this._searchStore;
+      },
+    },
+  },
   data() {
     return {
       blockClassName: 'ais-powered-by',