Resolve "Loading animation for timetable object select on left side of timetables"

Closes #263 (closed)

aleksis/apps/chronos/frontend/components/SelectTimetable.vue

 <script>
 import timetableTypes from "./timetableTypes";
+import Mascot from "aleksis.core/components/generic/mascot/Mascot.vue";
 
 export default {
   name: "SelectTimetable",
+  components: {
+    Mascot,
+  },
   props: {
     value: {
       type: Object,
@@ -126,6 +130,14 @@ export default {
           type="list-item-avatar@10"
         />
       </template>
+      <template #no-results>
+        <div class="d-flex flex-column align-center justify-center">
+          <mascot type="searching" width="33%" min-width="250px" />
+          <div class="mb-2">
+            {{ $t("$vuetify.dataIterator.noResultsText") }}
+          </div>
+        </div>
+      </template>
     </v-data-iterator>
   </div>
 </template>