run HelloFullScrEx toy sample and see the exception :

*** unexpected PG access
java.lang.Exception: Stack trace
at java.lang.Thread.dumpStack(Thread.java:1249)
at javafx.scene.Node.impl_getPGNode(Node.java:1764)
at javafx.scene.Node.impl_updatePG(Node.java:445)
at javafx.scene.shape.Shape.impl_updatePG(Shape.java:718)
at javafx.scene.text.Text.impl_updatePG(Text.java:1329)
at com.sun.javafx.tk.quantum.OverlayWarning.createOverlayGroup(OverlayWarning.java:124)
at com.sun.javafx.tk.quantum.OverlayWarning.<init>(OverlayWarning.java:57)
at com.sun.javafx.tk.quantum.WindowStage.applyFullScreen(WindowStage.java:436)
at com.sun.javafx.tk.quantum.WindowStage.setVisible(WindowStage.java:354)
at javafx.stage.Window$13.invalidated(Window.java:704)
at javafx.beans.property.BooleanPropertyBase.markInvalid(BooleanPropertyBase.java:88)
at javafx.beans.property.BooleanPropertyBase.set(BooleanPropertyBase.java:122)
at javafx.stage.Window.setShowing(Window.java:744)
at javafx.stage.Window.show(Window.java:759)
at javafx.stage.Stage.show(Stage.java:129)