Dashboard widget can be linked to itself

Steps to reproduce:
1) create a new dashboard;
2) add map navigation tree widget and name it 'tree1'. Confirm changes;
3) add another map navigation tree widget and name it 'tree2'. Confirm changes;
4) now, without saving dashboard, open the configuration window of tree2 and change the widget type to Map.
5) Select 'Map navigation tree' as a Source type and select 'Tree2' in Filter field.
6) Save changes in Dashboard.

Result: Map widget is linked to itself.