[6.x] Fix uploading assets via Markdown fieldtype (#13782)

Author: duncanmcclean

resources/js/components/fieldtypes/markdown/MarkdownFieldtype.vue

@@ -17,7 +17,7 @@
                 <uploader
                     ref="uploader"
                     :enabled="assetsEnabled"
-                    :container="container"
+                    :container="container.id"
                     :path="folder"
                     @updated="uploadsUpdated"
                     @upload-complete="uploadComplete"

src/Http/Controllers/CP/Assets/AssetsController.php

@@ -13,6 +13,7 @@
 use Statamic\Contracts\Assets\AssetContainer as AssetContainerContract;
 use Statamic\Contracts\Assets\AssetFolder;
 use Statamic\Exceptions\AuthorizationException;
+use Statamic\Exceptions\NotFoundHttpException;
 use Statamic\Facades\Asset;
 use Statamic\Facades\AssetContainer;
 use Statamic\Facades\User;
@@ -85,6 +86,8 @@ public function store(Request $request)
 
         $container = AssetContainer::find($request->container);
 
+        throw_unless($container, NotFoundHttpException::class);
+
         $this->authorize('store', [AssetContract::class, $container]);
 
         $validationRules = collect($container->validationRules())