**Steps to replicate the issue** (include links if applicable):
* Load https://ckb.wikipedia.org/w/rest.php/v1/page/%D8%AF%D8%A7%DA%95%DB%8E%DA%98%DB%95%3ACOVID-19_data%2Fdata/html
**What happens?**:
* Get status 500
**What should have happened instead?**:
* Get rendered content of <https://ckb.wikipedia.org/w/index.php/%D8%AF%D8%A7%DA%95%DB%8E%DA%98%DB%95%3ACOVID-19_data%2Fdata>, or at least dummy content per T311728.
**Notes:**
* Note that the page in question uses the JSON content model.
==Logstash==
* reqId: befbc706-3204-43a7-8955-bc1804b69b8b
* exception.message: Failed to find content language in page bundle data
```
from /srv/mediawiki/php-1.42.0-wmf.20/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(614)
#0 /srv/mediawiki/php-1.42.0-wmf.20/includes/Rest/Handler/Helper/HtmlOutputRendererHelper.php(629): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->getHtmlOutputContentLanguage()
#1 /srv/mediawiki/php-1.42.0-wmf.20/includes/Rest/Handler/PageHTMLHandler.php(137): MediaWiki\Rest\Handler\Helper\HtmlOutputRendererHelper->putHeaders(MediaWiki\Rest\Response, boolean)
#2 /srv/mediawiki/php-1.42.0-wmf.20/includes/Rest/SimpleHandler.php(40): MediaWiki\Rest\Handler\PageHTMLHandler->run(string)
```