Suppress notice message when guid isn't supplied in Module\Admin\Item\Source

- https://github.com/friendica/friendica/issues/9252#issuecomment-740052103

src/Module/Admin/Item/Source.php

@@ -33,7 +33,7 @@ class Source extends BaseAdmin
 	{
 		parent::content($parameters);
 
-		$guid = basename($_REQUEST['guid'] ?? '') ?: $parameters['guid'];
+		$guid = basename($_REQUEST['guid'] ?? $parameters['guid'] ?? '');
 
 		$source = '';
 		$item_uri = '';