New direct chat created even though existing

### Steps to reproduce

In a room, I click on the picture of a member and then I click on the "Direct chat" link.

### What happened?

### What did you expect?
It switch to the already existing direct chat between me and this member as it does on the android element app
### What happened?
it creates a new direct chat between me and this member

### Operating system

Debian 10 and Debian 11

### Application version

Version de Element : 1.8.5 Version de Olm : 3.2.3

### How did you install the app?

from website element.io

### Homeserver

matrix.leprette.fr

### Have you submitted a rageshake?

No

Start by reproducing the flow in the web app: open a room, select a member, and choose “Direct chat.” Trace how that action finds or creates a direct chat, then verify that completion reuses the existing conversation rather than creating another one; compare the behavior with the Android app if useful.

Written by the indexing model from the issue text.