Reproduce:

1. Do not log in
2. View https://meta.wikimedia.org/wiki/Special:UrlShortener and input an URL to shorten
3. Click "Shorten" 11 times

Expected:

Error message will be output to the "Shortened URL" box. It is already returned by API:

{"error":{"code":"urlshortener-ratelimit","info":"Please wait some time before shortening more URLs.","*":"See https://meta.wikimedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}}

Actual:

The "Shortened URL" box shows "[object Object]"