FULL PRODUCT VERSION :
openjdk version "1.8.0_131"
OpenJDK Runtime Environment (build 1.8.0_131-8u131-b11-0ubuntu1.17.04.1-b11)
OpenJDK 64-Bit Server VM (build 25.131-b11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
4.10.0-19-generic #21-Ubuntu SMP Thu Apr 6 17:04:57 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
The NPE occures during a Scene change. In detaill im Switsching from a maximized scene to smaller Scene (I think this is important, but Im not sure).
The Stage remains maximized but the smaller scene is rendered only in the top left corner.
It seems to be Linux specific as it runs fine on windows 10. Here is the Stacktrace:

Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.MenuBarSkin.lambda$new$6(MenuBarSkin.java:304)
at javafx.event.WeakEventHandler.handle(WeakEventHandler.java:79)
at com.sun.javafx.event.CompositeEventHandler$WeakEventFilterRecord.handleCapturingEvent(CompositeEventHandler.java:312)
at com.sun.javafx.event.CompositeEventHandler.dispatchCapturingEvent(CompositeEventHandler.java:98)
at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:223)
at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:180)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchCapturingEvent(CompositeEventDispatcher.java:43)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:52)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$5(GtkApplication.java:139)
at java.lang.Thread.run(Thread.java:748)


The NPE occures when the EventHandler is triggered

mouseEventHandler = t -> {
            if (!container.localToScreen(container.getLayoutBounds()).contains(t.getScreenX(), t.getScreenY())) {
                unSelectMenus();
            }
        };

becouse 'localToScreen()' returns null. p1 to p8 in the localToScreen method are null although the localBounds instance seems to hold valid values. As in the JavaDoc written the method is returning null becouse the node is not in a Window.
The mouseEventHandler in com.sun.javafx.scene.control.skin.MenuBarSkin should check if the result of localToScreen is null.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
The bug was observed in a rather big Application with different UI Elments. I tried to build a minimal Example but was unable to trigger the bug.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.MenuBarSkin.lambda$new$6(MenuBarSkin.java:304)
at javafx.event.WeakEventHandler.handle(WeakEventHandler.java:79)
at com.sun.javafx.event.CompositeEventHandler$WeakEventFilterRecord.handleCapturingEvent(CompositeEventHandler.java:312)
at com.sun.javafx.event.CompositeEventHandler.dispatchCapturingEvent(CompositeEventHandler.java:98)
at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:223)
at com.sun.javafx.event.EventHandlerManager.dispatchCapturingEvent(EventHandlerManager.java:180)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchCapturingEvent(CompositeEventDispatcher.java:43)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:52)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$ClickGenerator.postProcess(Scene.java:3470)
at javafx.scene.Scene$ClickGenerator.access$8100(Scene.java:3398)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3766)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:380)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:294)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:416)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:415)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.lambda$null$5(GtkApplication.java:139)
at java.lang.Thread.run(Thread.java:748)

REPRODUCIBILITY :
This bug can be reproduced always.