Thread summary shows non-existing messages

[frakic]

Steps to reproduce

1. Where are you starting? What can you see?
   -I have threads turned on
2. What do you click?
   -I click the "Reply in thread" icon on someone else's message (i.e. start a thread)
3. More steps…
   -Thread summary immediately shows 1 reply, even though I haven't sent anything yet
   -If i send my reply, thread summary shows 2 replies

Outcome

What did you expect?

I expected the thread summary to appear only after I've sent the first message and also to show correct number of replies.

What happened instead?

Thread summary with 1 reply appears before the first threaded message is sent and shows 2 replies when there is 1.

Operating system

Windows 11 Home 21H2

Application version

Element version: 1.10.12 Olm version: 3.2.8

How did you install the app?

From https://element.io/get-started#nightly

Homeserver

matrix.org

Will you send logs?

Yes

[robintown]

Fixed on develop by matrix-org/matrix-js-sdk#2369