DM'ing yourself and leaving the room makes you unable to forget the room

### Description

When a room is started by sending a direct message to yourself, the room is created and has the name "Empty room", and the user is the only one in it. Upon leaving the room, it will go to the "Historical" tab. clicking "forget room" in the room options does not cause the room to be removed. Trying to rejoin the room displays an error message.


### Steps to reproduce

- click the "start chat" button under the "people" tab
- enter your own username and start the room
- go to the newly created room and leave it
- room will now be under the "historical" tab
- try to join the room or forget it

### Version information

- **Platform**: web
- **Browser**: Mozilla Firefox 78.7.0esr
- **OS**: Gentoo Linux
- **URL**: [https://app.element.io/](url)