Expected Behavior
Show cursor markers of participants in the editor.
Actual Behavior
The cursor marker of the participant which has left still shown.

Steps to Reproduce
It shows sometimes
- open a file as userA,
- open a file as userB,
- put the two users' cursor at the same position in each editor (type sth.)
- close/leave one user's editor
- open the same project file
- extra cursor marker appears at the previous cursor position

Expected Behavior
Show cursor markers of participants in the editor.
Actual Behavior
The cursor marker of the participant which has left still shown.
Steps to Reproduce
It shows sometimes