The giant `Add discussion` button and "There are no discussions on this page" message appears on pages in talk namespaces even when content model is not `wikitext`.
==== Steps to Reproduce:
* Go to a page in one of the talk namespace.
* Change it's content model from Wikitext to something else.
====Actual Results:
* The big `Add discussion` button is displayed even if the page content model is not `wikitext`. And a message stating "There are no discussions on this page" is displayed.
==== Expected Results:
* The big `Add discussion` button is not shown if the page content model is not `wikitext`. No message appears.
==== Screenshot
Screenshot of https://commons.m.wikimedia.beta.wmflabs.org/wiki/Talk:Test when the content model of the page is json.
{F31093330}
==== QA steps
[] Go to https://commons.m.wikimedia.beta.wmflabs.org/wiki/Talk:Test
[] Ensure that there is not a "There are no discussions on this page" message or "Active discussions" message anywhere on the page.
[] Ensure that there is not a "Add discussion" button on the page.