Newly left rooms can crash clients

[microchipster]

Description

Described in more detail here:
#19651
element-hq/element-x-android#6532
element-hq/element-x-ios#5354

I don't have a proper development environment to test these, but figured the PRs are more communicative.

Steps to reproduce

See PRs for details.

Homeserver

custom, up to date with https://github.com/spantaleev/matrix-docker-ansible-deploy

Synapse Version

1.150.0

Installation Method

Docker (matrixdotorg/synapse)

Database

postgres

Workers

Multiple workers

Platform

https://github.com/spantaleev/matrix-docker-ansible-deploy on VPS

Configuration

No response

Relevant log output

See PRs.

Anything else that would be useful to know?

Crashes clients in a really bad way.