Make sure that when the returned RoomMember in NeochatRoomMember is empty that displayname and similar functions return the member Matrix ID
BUG: 491025
The intention is that NeochatRoomMember can be created passed to QML and then be fully managed by it. It effectively just grabs the current RoomMember, calls the correct function then discards it so that we don't end up trying to access an already deleted state event.