Merge pull request #16993 from owncloud/verify-if-path-exists

[master] Verify if path exists

apps/files_sharing/ajax/publicpreview.php

@@ -63,6 +63,13 @@ $view = new \OC\Files\View('/' . $userId . '/files');
 
 $pathId = $linkedItem['file_source'];
 $path = $view->getPath($pathId);
+
+if($path === null) {
+	\OC_Response::setStatus(\OC_Response::STATUS_NOT_FOUND);
+	\OC_Log::write('core-preview', 'Could not resolve file for shared item', OC_Log::WARN);
+	exit;
+}
+
 $pathInfo = $view->getFileInfo($path);
 $sharedFile = null;