I can see why he got the error when he hit the same button as me, but the other places don’t seem directly related. For example, the chat icon at the top doesn’t use the same way to redirect to the chat page.
I could still delete all the channels (even though I got errors with Staff and General).
I created again only one public channel General, and I still get the error:
My dev instance is up to date without any plugins/themes.
I will reset my dev instance; I don’t know if something went wrong with the DB or something else.
To give another example of a different context, I upgraded a production Discourse from 3.2.0-dev4 to the latest (which includes the fix), and the error happens as well. (it was working fine before the upgrade)