java.lang.IllegalArgumentException: A node selection cannot contain nodes ([JFrame]) not underneath the root ().
        at org.openide.explorer.ExplorerManager.checkUnderRoot(ExplorerManager.java:561)
        at org.openide.explorer.ExplorerManager.access$300(ExplorerManager.java:87)
        at org.openide.explorer.ExplorerManager$1AtomicSetSelectedNodes.checkArgumentIsValid(ExplorerManager.java:232)
        at org.openide.explorer.ExplorerManager$1AtomicSetSelectedNodes.run(ExplorerManager.java:265)
        at org.openide.util.Mutex.readAccess(Mutex.java:362)
        at org.openide.explorer.ExplorerManager.setSelectedNodes(ExplorerManager.java:272)
        at org.netbeans.modules.form.ComponentInspector.setSelectedNodes(ComponentInspector.java:333)
        at org.netbeans.modules.form.FormDesigner.updateComponentInspector(FormDesigner.java:1373)
        at org.netbeans.modules.form.FormDesigner.setSelectedComponent(FormDesigner.java:901)
        at org.netbeans.modules.form.HandleLayer.selectComponent(HandleLayer.java:690)
        at org.netbeans.modules.form.HandleLayer.mousePressed(HandleLayer.java:1607)
        at java.awt.Component.processMouseEvent(Component.java:6038)
        at javax.swing.JComponent.processMouseEvent(JComponent.java:3265)
        at java.awt.Component.processEvent(Component.java:5806)
        at java.awt.Container.processEvent(Container.java:2058)
        at java.awt.Component.dispatchEventImpl(Component.java:4413)
        at java.awt.Container.dispatchEventImpl(Container.java:2116)
        at java.awt.Component.dispatchEvent(Component.java:4243)
        at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4322)
        at java.awt.LightweightDispatcher.processMouseEvent(LightweightDispatcher.java:3983)
        at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:3916)
        at java.awt.Container.dispatchEventImpl(Container.java:2102)
        at java.awt.Window.dispatchEventImpl(Window.java:2440)
        at java.awt.Component.dispatchEvent(Component.java:4243)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:599)
        at org.netbeans.core.TimeableEventQueue.dispatchEvent(TimeableEventQueue.java:104)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:273)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:183)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:173)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:168)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:160)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:121)