Steps to reproduce:
 - start scenebuilder
 - add a Button to content pane
 - add context menu to button
 - context menu will have 1 menu item by default
 - insert Menu into Context Menu
 - menu will be added with a menu item
 - click on menu item in hierarchy panel
Scene Builder will hang. There will be an exception in the log:

java.lang.NullPointerException
at javafx.scene.control.MenuItem$3.getNode(MenuItem.java:603)
at com.oracle.javafx.authoring.css.CssUtils.getCssInfo(CssUtils.java:514)
at com.oracle.javafx.authoring.css.CssUtils.isCssRuled(CssUtils.java:564)
at com.oracle.javafx.authoring.panels.TabContentMaker.makePlatformProperties(TabContentMaker.java:342)
at com.oracle.javafx.authoring.panels.TabContentMaker.access$700(TabContentMaker.java:43)
at com.oracle.javafx.authoring.panels.TabContentMaker$2.call(TabContentMaker.java:238)
at com.oracle.javafx.authoring.panels.TabContentMaker$2.call(TabContentMaker.java:234)
at com.oracle.javafx.authoring.metadata.PropertySet.getProperties(PropertySet.java:43)
at com.oracle.javafx.authoring.panels.SlotEditorMaker.fillLabelValueContainer(SlotEditorMaker.java:276)
at com.oracle.javafx.authoring.panels.SlotEditorMaker.makeLabelValueContainer(SlotEditorMaker.java:270)
at com.oracle.javafx.authoring.panels.ElementPanel.makeLabelValueContainer(ElementPanel.java:322)
at com.oracle.javafx.authoring.panels.TabPanel.buildLabelValueContainer(TabPanel.java:264)
at com.oracle.javafx.authoring.panels.TabPanel.buildLabelValueBun(TabPanel.java:242)
at com.oracle.javafx.authoring.panels.TabPanel.buildLabelValuePane(TabPanel.java:224)
at com.oracle.javafx.authoring.panels.TabPanel.doBuildLabelValuePane(TabPanel.java:208)
at com.oracle.javafx.authoring.panels.TabPanel.buildPane(TabPanel.java:167)
at com.oracle.javafx.authoring.panels.TabPanel.buildPane(TabPanel.java:136)
at com.oracle.javafx.authoring.panels.TabPanel.access$300(TabPanel.java:41)
at com.oracle.javafx.authoring.panels.TabPanel$3.run(TabPanel.java:119)
at com.oracle.javafx.authoring.util.Utils$NextFrameTimer.handle(Utils.java:531)
at com.sun.scenario.animation.AbstractMasterTimer.timePulseImpl(AbstractMasterTimer.java:376)
at com.sun.scenario.animation.AbstractMasterTimer$MainLoop.run(AbstractMasterTimer.java:289)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:456)
at com.sun.javafx.tk.quantum.QuantumToolkit$9.run(QuantumToolkit.java:329)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:76)
at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:82)
at java.lang.Thread.run(Thread.java:679)