no way to mark notification as done for a chat which no longer exists.

### Steps to reproduce

1. start private chat with an user
2. other user requests verification
3. you see the dot next to the bell icon in the upper right
4. both leave the chat.
5. the notification is still there for the verification but you cant really mark it was read/done.
6. if you click onto the notification it does "Empty room (was otherusername) can't be previewed. Do you want to join it? (join discussion button)"
7. opening a new chat with the same user and doing the verification there does not mark the old "wants to verify you" notification as done.

### Outcome

#### What did you expect?

either the notifications associated to the chat, which you just left, should be marked as done or I should have a method to mark it as done.

#### What happened instead?

i am stuck with a notification which i can not discard.

### Operating system

openSUSE Tumbleweed

### Browser information

Vivaldi Stable

### URL for webapp

_No response_

### Application version

v1.11.106

### Homeserver

_No response_

### Will you send logs?

if needed.