/topic command gives no feedback, can send multiple times

### Steps to reproduce

Use `/topic` to set the topic in a room, press enter multiple times quickly (before the http request to set the topic completes, so depends a bit on homeserver speed)

### Outcome

#### What did you expect?
Topic to change once, input to clear upon hitting enter; possibly with local-echo of the change before the request actually completes

#### What happened instead?
Multiple topic state events are sent, input only gets cleared when the (first) event is sent. No feedback at all that you've started sending the request, because nothing changes in the UI.

### Operating system

NixOS

### Browser information

Firefox 135.0b4 (64-bit)

### URL for webapp

self-hosted

### Application version

Element version: 1.11.89

### Homeserver

pixie.town Synapse 1.121.1 (with rather poor performance...)

### Will you send logs?

No