Missing "Add" actions in the "Security" app -> "Users" tab after clean install

Steps to reproduce

1. Install 6.2.15 or 6.2.16 from scratch
2. Go to the "Security" app -> "Users" tab
3. Try to add a new user or folder there

Expected results

You click the "Add user" or "Add folder" actions and create what you need.

Actual results

"Add" actions are missing

The log shows this warning:

WARN agnolia.ui.workbench.tree.HierarchicalJcrContainer: Cannot retrieve root item id’s: javax.jcr.PathNotFoundException: /admin

Workaround

Add the "admin" node into the "users" workspace via JCR.

Development notes