Merge pull request #13188 from owncloud/add-check-if-user-is-logged-in

Add check if user is logged-in

apps/files_versions/ajax/getVersions.php

 <?php
+OCP\JSON::checkLoggedIn();
+OCP\JSON::callCheck();
 OCP\JSON::checkAppEnabled('files_versions');
 
 $source = $_GET['source'];

apps/files_versions/ajax/rollbackVersion.php

 <?php
 
+OCP\JSON::checkLoggedIn();
 OCP\JSON::checkAppEnabled('files_versions');
 OCP\JSON::callCheck();