SearchForm: fix inconsistent/mixed search results

- SearchForm.vue: route Enter key through submit() (native form submit
  interception) so it behaves like the button; fix autocomplete array
  mutation during iteration in the typed watcher.
- Base.vue: parse terms consistently in beforeRouteUpdate; render items
  via displayedItems (drops sparse holes); only mount infinite-loading
  after the first page and reset it per search via :identifier.
- search store: guard against stale async responses (searchId); place
  each page at its offset instead of concatenating in arrival order,
  which mixed pages when a later page resolved first.

web/themes/custom/materiotheme/vuejs/components/Pages/Base.vue

@@ -11,13 +11,14 @@
         <span>{{ $t('default.Loading…') }}</span>
       </div>
       <ul v-else>
-        <li v-for="item in items" v-bind:key="item.id">
+        <li v-for="item in displayedItems" v-bind:key="item.id">
           <Card v-if="item.bundle == 'materiau'" :item="item"/>
           <CardThematique v-if="item.bundle == 'thematique'" :item="item"/>
         </li>
       </ul>
       <infinite-loading
-        v-if="count > limit"
+        v-if="count > limit && displayedItems.length >= limit"
+        :identifier="searchId"
         @infinite="nextPage"
       >
         <div slot="no-more">No more results</div>
@@ -48,8 +49,14 @@ export default {
       searchinfos: state =>  state.Search.infos,
       count: state => state.Search.count,
       noresults: state => state.Search.noresults,
-      limit: state => state.Search.limit
-    })
+      limit: state => state.Search.limit,
+      searchId: state => state.Search.searchId
+    }),
+    // items is a sparse array (pages placed by offset); drop the holes left by
+    // pages that returned fewer results than the limit before rendering.
+    displayedItems () {
+      return this.items.filter(Boolean)
+    }
   },
   methods: {
     ...mapActions({
@@ -98,7 +105,10 @@ export default {
     // todo text field of search form is not emptying on clicking on base after a search
     // this.$store.commit('Search/setKeys', to.query.keys)
     if (to.query.hasOwnProperty('terms')) {
-      this.$store.commit('Search/setTerms', to.query.terms)
+      // to.query.terms is a raw JSON string (see SearchForm.submit) and must be
+      // parsed like in created(), otherwise getResults() double-encodes it and
+      // the backend silently drops the terms (less relevant results).
+      this.$store.commit('Search/setTerms', JSON.parse(to.query.terms))
     }else{
       this.$store.commit('Search/reSetTerms')
     }