Loading an already-joined room can time out

[dbkr]

Describe the bug
Sometimes if you load element call with a URL to a room you've participated in previously, it will time out trying to load the room. This is because the user is joined to it as far as the homeserver is concerned but somehow the room is not present in the client's data store (presumably missed getting saved to indexeddb somehow). The client tries to join the room and then waits for it to come down the sync, which of course it never does because it the user was already in it.

To Reproduce
Unclear