The tiny attached code triggers the stack below (FX 8 b92, seen on Mac and Win):

Caused by: java.lang.NullPointerException
at com.sun.javafx.scene.control.skin.MenuBarSkin.<init>(MenuBarSkin.java:295)
at javafx.scene.control.MenuBar.createDefaultSkin(MenuBar.java:156)
at javafx.scene.control.Control.impl_processCSS(Control.java:863)
at javafx.scene.Parent.impl_processCSS(Parent.java:1191)
at javafx.scene.Node.processCSS(Node.java:8515)
at javafx.scene.Scene.doCSSPass(Scene.java:540)
at javafx.scene.Scene.preferredSize(Scene.java:1578)
at javafx.scene.Scene.doCSSLayoutSyncForSnapshot(Scene.java:1197)
at javafx.scene.Node.doSnapshot(Node.java:1755)
at javafx.scene.Node.snapshot(Node.java:1865)
at javafxapplicationpasglop.JavaFXApplicationPasGlop.start(JavaFXApplicationPasGlop.java:24)
at com.sun.javafx.application.LauncherImpl$5.run(LauncherImpl.java:810)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:260)
at com.sun.javafx.application.PlatformImpl$5$1.run(PlatformImpl.java:226)
at com.sun.javafx.application.PlatformImpl$5$1.run(PlatformImpl.java:223)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$5.run(PlatformImpl.java:223)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)