fix(json-api-express): make sure response status is a number

Regardless of Error instance has `status` property as string, convert it to number for `res.status()`.

Fixes #369

src/middlewares/json-api-express.ts

@@ -51,7 +51,7 @@ export default function jsonApiExpress(
     try {
       await authenticate(appInstance, req);
     } catch (error) {
-      res.status(error.status).json(convertErrorToHttpResponse(error));
+      res.status(+error.status).json(convertErrorToHttpResponse(error));
       return next();
     }