Fix presence indicators not showing without cache

[DLCSharp]

Tested on Element Web v1.12.12, local dev server.
This issue does not happen on v1.12.2. There were changes to how the room list is rendered, which I believe to be impacting load timing.

Summary

Presence indicators in the DM room list do not appear on initial login (when the room is not in the sync cache).
When a room gets put in cache - for example by sending a message in the room -, the presence indicator for this room will appear on next refresh and update correctly from this point on.

Root cause

During initial sync, RoomMember.user is not yet linked to the User object when the room list renders. The usePresence hook reads presence from member.user, which is null at that point.
The user object exists in client store (client.getUser()), but the hook doesn't fall back to it.

From my understanding, the room list renders before the SDK can link RoomMember.user which causes this issue. On subsequent loads, the user objects are available early enough for the linking to succeed thanks to the cache.

So, we end up with at least some rooms not having their presence rendered :

Fixes

• In getPresence, we fall back to client.getUser(member.userId) when member.user is not linked.
• We also listen to the client-level UserEvent.Presence to catch presence update events when member.user is null since the event listener cannot subscribe to it.

With these fixes, we end up with all 1:1 DM rooms having their presence rendered :

Notes

I believe the same linking issue also affects DM avatars on the first page load since they only render after a subsequent reload in Web.
If I am correct, the proper long-term fix should probably be in the SDK itself.

[CLAassistant]

All committers have signed the CLA.

[t3chguy]

Looks sane, thanks

[DLCSharp]

No problem, happy to be of help