Master node bug.
1. Open the master node GUI.
2. In the filter of available nodes select only one node, for instance "node1".
3. Go to the Dashboard filter configuration.
4. Press Add to add a group.
5. All nodes will be available for selection, but they should not (see screenshot #1).

Child node bug.
1. Open the child node GUI.
2. Go to the Dashboard filter configuration.
3. Press Add to add a group.
4. Master node will be available for selection, but they should not.
4.1 of course after selecting Node1 (see screenshot #2) no any groups will be shown because master's groups are missing in the child's database.