Site Editor: Avoid previous content flash when a new template is crea…

…ted (#40841)

* Site Editor: Avoid previous content flash when a new template is created
* Pass slug

packages/edit-site/src/components/add-new-template/new-template.js

@@ -37,6 +37,7 @@ import { store as noticesStore } from '@wordpress/notices';
  * Internal dependencies
  */
 import { useHistory } from '../routes';
+import { store as editSiteStore } from '../../store';
 
 const DEFAULT_TEMPLATE_SLUGS = [
  'front-page',
@@ -86,6 +87,7 @@ export default function NewTemplate( { postType } ) {
  );
  const { saveEntityRecord } = useDispatch( coreStore );
  const { createErrorNotice } = useDispatch( noticesStore );
+ const { setTemplate } = useDispatch( editSiteStore );
 
  async function createTemplate( { slug } ) {
  try {
@@ -106,6 +108,9 @@ export default function NewTemplate( { postType } ) {
  { throwOnError: true }
  );
 
+ // Set template before navigating away to avoid initial stale value.
+ setTemplate( template.id, template.slug );
+
  // Navigate to the created template editor.
  history.push( {
  postId: template.id,