BUG: "Continue editing" button is visible, when a user is not able to edit

[Comoque1]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Go to https://sandbox-alkem.io/e2s/challenges/nocallouts with 2 users with rights to modify the WB (in this case single user WB)
2. The user who opens the WB first, sees the control bar
3. The user who opens the WB second:
   1. doesn't see control bar - OK
   2. sees "Continue editing" button, which doesn't work, until the user become the only one available on the WB

Expected behavior "Continue editing" button becomes visible, when user becomes the only one on the WB OR TBD