getRelativePath can return null

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

lib/private/Files/Node/Folder.php

@@ -76,7 +76,7 @@ class Folder extends Node implements \OCP\Files\Folder {
 
 	/**
 	 * @param string $path
-	 * @return string
+	 * @return string|null
 	 */
 	public function getRelativePath($path) {
 		if ($this->path === '' or $this->path === '/') {

lib/public/Files/Folder.php

@@ -55,7 +55,7 @@ interface Folder extends Node {
 	 *
 	 * @param string $path absolute path of an item in the folder
 	 * @throws \OCP\Files\NotFoundException
-	 * @return string
+	 * @return string|null
 	 * @since 6.0.0
 	 */
 	public function getRelativePath($path);