Cloning dashboard which has navigation tree with visible unavailable maps, the new map contains previously hidden items.

Steps to reproduce:
1) Create navigation tree widget and add some map with submaps and which is not available to non-superadmin user. Check 'Show unavailable maps' in widget configuration window';
2) Log in as non-superadmin user and open dashboard with just created map navigation tree widget;
3) Observe that unavailable parent map is inactive and there is no arrows on the left side indicating about submaps;
4) Clone the dashboard.

Result: arrows are visible and user can open branch and see what submaps it contains.
Expected: tree should not differ from one which was before the dashboard was cloned.