Knock join UI sometimes show when synapse is slow or unresponsive on room join

### Steps to reproduce

Currently unclear. I am assuming it's an error code in the reverse proxy or synapse causes this. Alternatively, maybe it is that knock is the default fallback?

I _think_ I have seen it even with the knock labs feature, but I didn't get around to confirm this. So for now it's best to assume it needs to be enabled.

### Outcome

#### What did you expect?

It shows some kind of error as before knock was implemented.

#### What happened instead?

It shows the ask for join UI and lets you submit it regardless of if a room is knockable or not. (Also errors of this are not shown afterwards)

### Operating system

Fedora Silverblue 38

### Browser information

Firefox 118.0.2 (64-bit)

### URL for webapp

develop.element.io

### Application version

Version von Element: bce820729393-react-d0b44a541d4c-js-ce7b7bf44f4c Crypto version: Olm 3.2.14

### Homeserver

matrix.midnightthoughts.space

### Will you send logs?

No