(fix) /api route results in 500

add ignored _next parameter as express needs four parameters to supply err
introduced in e5b84d736831ff37fb4238a0edc9b178d3b81f38

server/index.js

@@ -142,7 +142,7 @@ app.use(calendarRoute);
 app.use(translationsRoute);
 app.use(subscriptionRoute);
 
-app.use(function (err, req, res) {
+app.use(function (err, req, res, _next) {
     console.error(formatError(err, req));
     res.status(500).send('Unexpected server error');
     req.db.close();