To reproduce run HelloWindowManager in toys/HelloWorld

#Stage1 ShowHide WINDOW_SHOWING
#Stage1 Focused changed to true
#Stage1 ShowHide WINDOW_SHOWN
#Popup1 ShowHide WINDOW_SHOWING
Exception in thread "JavaFX Application Thread" java.lang.StackOverflowError
at java.util.AbstractCollection.isEmpty(AbstractCollection.java:86)
at com.sun.javafx.collections.VetoableListDecorator.isEmpty(VetoableListDecorator.java:174)
at javafx.scene.Parent.impl_computeGeomBounds(Parent.java:1310)
at javafx.scene.Node.updateGeomBounds(Node.java:3466)
at javafx.scene.Node.getGeomBounds(Node.java:3419)
at javafx.scene.Node.getLocalBounds(Node.java:3401)
at javafx.scene.Node.updateTxBounds(Node.java:3479)
at javafx.scene.Node.getTransformedBounds(Node.java:3319)
at javafx.scene.Parent.recomputeBounds(Parent.java:1455)
at javafx.scene.Parent.impl_computeGeomBounds(Parent.java:1319)
at javafx.scene.Node.updateGeomBounds(Node.java:3466)
at javafx.scene.Node.getGeomBounds(Node.java:3419)
at javafx.scene.Node.impl_computeLayoutBounds(Node.java:3269)
at javafx.scene.Group.impl_computeLayoutBounds(Group.java:160)
at javafx.scene.Node$15.computeBounds(Node.java:3126)
at javafx.scene.Node$LazyBoundsProperty.get(Node.java:8775)
at javafx.scene.Node$LazyBoundsProperty.get(Node.java:8745)
at javafx.scene.Node.getLayoutBounds(Node.java:3141)
at javafx.stage.PopupWindow.syncWithRootBounds(PopupWindow.java:478)
at javafx.stage.PopupWindow.access$000(PopupWindow.java:91)
at javafx.stage.PopupWindow$1.invalidated(PopupWindow.java:106)