Address dynamic class property deprecation warnings

models/AssetIterator.php

@@ -12,6 +12,7 @@ class AssetIterator extends Asset
 	private $res_assets;
 	private $res_meta;
 	private $res_thumbs;
+	private Database $db;
 
 	protected function __construct($res_assets, $res_meta, $res_thumbs, $return_format)
 	{