404 error "All Classes", template=online

What steps will reproduce the problem?

Create api doc with template online, display inside yii2.
Click "All Classes" link on top of any page (example here).

What's expected?

https://www.yiiframework.com/doc/api/2.0/index

What do you get instead?

https://www.yiiframework.com/doc/api/2.0/index.html

Additional info

Possibly a bug in https://github.com/yiisoft-contrib/yiiframework.com, perhaps in the template online. As I thought the template might be the issue, I report bug here.

[samdark]

yiisoft-contrib/yiiframework.com#386

[samdark]

It is a template issue, indeed.