ldapserver: fix crash when app not found

src/ldapserver.js

@@ -510,6 +510,7 @@ async function userSearchSftp(req, res, next) {
 
     const [error, app] = await safe(apps.getByFqdn(appFqdn));
     if (error) return next(new ldap.OperationsError(error.message));
+    if (!app) return next(new ldap.OperationsError('Invalid app'));
 
     // only allow apps which specify "ftp" support in the localstorage addon
     if (!safe.query(app.manifest.addons, 'localstorage.ftp.uid')) return next(new ldap.UnavailableError('Not supported'));