(See Environment first)
Drop a Button.
Move it in the Contne Panel 2 or 3 times.
SB hang, with the following NPE:
Exception in thread "JavaFX Application Thread" java.lang.NullPointerException
    at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.activateGesture(EditModeController.java:773)
    at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.mousePressedOnGlassLayer(EditModeController.java:617)
    at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.access$300(EditModeController.java:88)
    at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController$4.handle(EditModeController.java:467)
    at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController$4.handle(EditModeController.java:464)
    at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
    at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
    at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
    at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
    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:203)
    at javafx.scene.Scene$MouseHandler.process(Scene.java:3659)
    at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3384)
    at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1652)
    at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2443)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:314)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:243)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:345)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:523)
    at com.sun.glass.ui.View.notifyMouse(View.java:889)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.access$200(GtkApplication.java:48)
    at com.sun.glass.ui.gtk.GtkApplication$6$1.run(GtkApplication.java:149)
    at java.lang.Thread.run(Thread.java:744)