Minimising the app while trying to join a sub-space causes the app to crash

### Steps to reproduce

1. Where are you starting? What can you see?
-I've received an invitation link to a sub-space
2. What do you click?
-I visit the link and proceed to join the sub-space
3. More steps…
-While waiting to join, I minimise the app and do something else
-When I switch back to the app, I can see the crash report screen

Rageshake: https://github.com/matrix-org/element-android-rageshakes/issues/39795

### Outcome

#### What did you expect?
I expected to resume my work in the app.
#### What happened instead?
The app crashed instead.

### Your phone model

Samsung Galaxy A40

### Operating system version

Android 11

### Application version and app store

Element version: 1.4.25 [40104252] (G-b9267), olm version: 3.2.12

### Homeserver

matrix.org

### Will you send logs?

Yes

### Are you willing to provide a PR?

No