chore: improve typing for SharedStorage::$storage

Signed-off-by: Robin Appelman <robin@icewind.nl>

Author: icewind1991

apps/files_sharing/lib/SharedStorage.php

@@ -100,6 +100,12 @@ class SharedStorage extends \OC\Files\Storage\Wrapper\Jail implements ISharedSto
 
 	private static int $initDepth = 0;
 
+	/**
+	 * @psalm-suppress NonInvariantDocblockPropertyType
+	 * @var ?\OC\Files\Storage\Storage $storage
+	 */
+	protected $storage;
+
 	public function __construct($arguments) {
 		$this->ownerView = $arguments['ownerView'];
 		$this->logger = \OC::$server->get(LoggerInterface::class);
@@ -135,6 +141,9 @@ private function getSourceRootInfo() {
 		return $this->sourceRootInfo;
 	}
 
+	/**
+	 * @psalm-assert \OC\Files\Storage\Storage $this->storage
+	 */
 	private function init() {
 		if ($this->initialized) {
 			if (!$this->storage) {