How to reproduce:
1. Use http://jre.us.oracle.com/java/re/javafx/8.0/prepromote/ea/b103/bundles/
2. Launch Modena:
jdk1.8.0/bin/java -jar qa-samples/Modena.jar
3. Click on Caspian button to reproduce the exception.

root@egtc-HP-Pro-3005-Microtower-PC:~/Desktop/swat/javafx-samples-8.0.0-ea# /root/Desktop/swat/jdk1.8.0/bin/java -jar Modena.jar
MODENA_EMBEDDED_STYLESHEET_URL = jar:file:/root/Desktop/swat/jdk1.8.0/jre/lib/ext/jfxrt.jar!/com/sun/javafx/scene/control/skin/modena/modena-embedded-performance.css
baseColor = null
accentColor = null
backgroundColor = null
baseColor = null
accentColor = null
backgroundColor = null
node = ComboBox@179fd94[styleClass=combo-box-base combo-box] node.lookup(.arrow-button) = null
node = ComboBox@f4ee09[styleClass=combo-box-base combo-box] node.lookup(.arrow-button) = null
node = ComboBox@69a972[styleClass=combo-box-base combo-box] node.lookup(.text-field) = null
node = SplitMenuButton@3f2ac3[styleClass=split-menu-button]'hover' node.lookup(.label) = null
node = SplitMenuButton@bdb4c2[styleClass=split-menu-button]'armed' node.lookup(.label) = null
node = SplitMenuButton@9ffcb6[styleClass=split-menu-button]'arrow hover' node.lookup(.arrow-button) = null
node = Slider@1a397da[styleClass=slider] node.lookup(.thumb) = null
node = Slider@8162e0[styleClass=slider] node.lookup(.thumb) = null
node = Slider@f55431[styleClass=slider] node.lookup(.thumb) = null
node = Slider@58e24a[styleClass=slider] node.lookup(.thumb) = null
node = Slider@1f1e435[styleClass=slider] node.lookup(.thumb) = null
node = Slider@ef03ff[styleClass=slider] node.lookup(.thumb) = null
node = ScrollBar@a0f867[styleClass=scroll-bar] node.lookup(.decrement-button) = null
node = ScrollBar@ffca2c[styleClass=scroll-bar] node.lookup(.decrement-button) = null
node = ScrollBar@8cd89f[styleClass=scroll-bar] node.lookup(.thumb) = null
node = ScrollBar@1f16d8f[styleClass=scroll-bar] node.lookup(.thumb) = null
node = TabPane@15f8a33[styleClass=tab-pane] node.lookup(.tab) = null
node = TabPane@b855e0[styleClass=tab-pane floating] node.lookup(.tab) = null
node = TabPane@c40eef[styleClass=tab-pane] node.lookup(.tab) = null
node = TabPane@8989bd[styleClass=tab-pane floating] node.lookup(.tab) = null
node = TabPane@b8f800[styleClass=tab-pane] node.lookup(.tab) = null
node = TabPane@7e9629[styleClass=tab-pane floating] node.lookup(.tab) = null
node = TabPane@158b2cd[styleClass=tab-pane] node.lookup(.tab) = null
node = TabPane@1d08e0c[styleClass=tab-pane floating] node.lookup(.tab) = null
node = Accordion@1283fbe[styleClass=accordion] node.lookup(.titled-pane) = null
node = Accordion@cfa2b1[styleClass=accordion] node.lookup(.titled-pane) = null
java.lang.IndexOutOfBoundsException: Index: 1, Size: 0
at java.util.ArrayList.rangeCheck(ArrayList.java:638)
at java.util.ArrayList.get(ArrayList.java:414)
at modena.SamplePageHelpers$3.run(SamplePageHelpers.java:279)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:285)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:282)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:282)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)
Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: The owner node needs to be associated with a window
at javafx.stage.PopupWindow.show(PopupWindow.java:332)
at javafx.scene.control.ContextMenu.doShow(ContextMenu.java:281)
at javafx.scene.control.ContextMenu.show(ContextMenu.java:271)
at modena.SamplePageHelpers$4.run(SamplePageHelpers.java:307)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:285)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:282)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:282)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)
Exception in thread "JavaFX Application Thread" java.lang.IllegalArgumentException: The owner node needs to be associated with a window
at javafx.stage.PopupWindow.show(PopupWindow.java:332)
at javafx.scene.control.ContextMenu.doShow(ContextMenu.java:281)
at javafx.scene.control.ContextMenu.show(ContextMenu.java:271)
at modena.SamplePageHelpers$4.run(SamplePageHelpers.java:307)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:285)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:282)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:282)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at modena.SameHeightTestController$1.run(SameHeightTestController.java:73)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:285)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:282)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:282)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
at modena.SimpleWindowPage$1.run(SimpleWindowPage.java:92)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:285)
at com.sun.javafx.application.PlatformImpl$6$1.run(PlatformImpl.java:282)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$6.run(PlatformImpl.java:282)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:47)
at com.sun.glass.ui.gtk.GtkApplication$5$1.run(GtkApplication.java:137)
at java.lang.Thread.run(Thread.java:724)