To reproduce:
add TabPane
add Tab either using Hierarchy or Content Panel
get the trace:

java.lang.NullPointerException
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.AbstractDecoration.startListeningToLayoutBounds(AbstractDecoration.java:178)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.driver.handles.TabHandles.startListeningToSceneGraphObject(TabHandles.java:102)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.AbstractDecoration$1.changed(AbstractDecoration.java:85)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.AbstractDecoration$1.changed(AbstractDecoration.java:79)
        at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:176)
        at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
        at javafx.beans.property.ReadOnlyObjectWrapper$ReadOnlyPropertyImpl.fireValueChangedEvent(ReadOnlyObjectWrapper.java:176)
        at javafx.beans.property.ReadOnlyObjectWrapper.fireValueChangedEvent(ReadOnlyObjectWrapper.java:142)
        at javafx.scene.Node$ReadOnlyObjectWrapperManualFire.fireSuperValueChangedEvent(Node.java:802)
        at javafx.scene.Node.invalidatedScenes(Node.java:851)
        at javafx.scene.Node.setScenes(Node.java:860)
        at javafx.scene.Parent$1.onChanged(Parent.java:276)
        at com.sun.javafx.collections.TrackableObservableList$1.onChanged(TrackableObservableList.java:48)
        at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:315)
        at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:72)
        at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
        at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
        at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
        at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
        at javafx.collections.ModifiableObservableListBase.add(ModifiableObservableListBase.java:155)
        at java.util.AbstractList.add(AbstractList.java:108)
        at com.sun.javafx.collections.VetoableListDecorator.add(VetoableListDecorator.java:200)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.updateHandles(EditModeController.java:399)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.updateHandles(EditModeController.java:341)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.mode.EditModeController.fxomDocumentDidRefreshSceneGraph(EditModeController.java:185)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.ContentPanelController.fxomDocumentDidRefreshSceneGraph(ContentPanelController.java:818)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.content.ContentPanelController.jobManagerRevisionDidChange(ContentPanelController.java:696)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.util.AbstractPanelController$3.changed(AbstractPanelController.java:187)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.util.AbstractPanelController$3.changed(AbstractPanelController.java:184)
        at com.sun.javafx.binding.ExpressionHelper$Generic.fireValueChangedEvent(ExpressionHelper.java:347)
        at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:80)
        at javafx.beans.property.IntegerPropertyBase.fireValueChangedEvent(IntegerPropertyBase.java:106)
        at javafx.beans.property.IntegerPropertyBase.markInvalid(IntegerPropertyBase.java:113)
        at javafx.beans.property.IntegerPropertyBase.set(IntegerPropertyBase.java:146)
        at com.oracle.javafx.scenebuilder.kit.editor.JobManager.incrementRevision(JobManager.java:211)
        at com.oracle.javafx.scenebuilder.kit.editor.JobManager.push(JobManager.java:76)
        at com.oracle.javafx.scenebuilder.kit.editor.drag.DragController.end(DragController.java:107)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.library.LibraryPanelController$8.handle(LibraryPanelController.java:621)
        at com.oracle.javafx.scenebuilder.kit.editor.panel.library.LibraryPanelController$8.handle(LibraryPanelController.java:616)
        at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
        at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
        at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
        at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
        at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
        at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
        at javafx.event.Event.fireEvent(Event.java:204)
        at javafx.scene.Scene$DnDGesture.processDropEnd(Scene.java:3017)
        at javafx.scene.Scene$DnDGesture.access$6800(Scene.java:2867)
        at javafx.scene.Scene$DragSourceListener.dragDropEnd(Scene.java:3252)
        at com.sun.javafx.tk.quantum.GlassScene$3$1.run(GlassScene.java:252)
        at com.sun.javafx.tk.quantum.GlassScene$3$1.run(GlassScene.java:247)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.tk.quantum.GlassScene$3.actionPerformed(GlassScene.java:247)
        at com.sun.glass.ui.Clipboard.actionPerformed(Clipboard.java:173)
        at com.sun.glass.ui.win.WinDnDClipboard.push(Native Method)
        at com.sun.glass.ui.win.WinSystemClipboard.pushToSystem(WinSystemClipboard.java:234)
        at com.sun.glass.ui.SystemClipboard.flush(SystemClipboard.java:51)
        at com.sun.glass.ui.ClipboardAssistance.flush(ClipboardAssistance.java:59)
        at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:274)
        at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1149)
        at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2911)
        at javafx.scene.Scene$DnDGesture.process(Scene.java:2972)
        at javafx.scene.Scene$DnDGesture.access$8400(Scene.java:2867)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3705)
        at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3414)
        at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1676)
        at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2467)
        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:526)
        at com.sun.glass.ui.View.notifyMouse(View.java:898)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.access$300(WinApplication.java:39)
        at com.sun.glass.ui.win.WinApplication$4$1.run(WinApplication.java:112)
        at java.lang.Thread.run(Thread.java:744)
Exception in thread "JavaFX Application Thread" Error:80de0001 in checkJavaException(env)
#
# A fatal error has been detected by the Java Runtime Environment:
#
# EXCEPTION_UNCAUGHT_CXX_EXCEPTION (0xe06d7363) at pc=0x752cc41f, pid=15884, tid=15796
#
# JRE version: Java(TM) SE Runtime Environment (8.0-b123) (build 1.8.0-ea-b123)
# Java VM: Java HotSpot(TM) Client VM (25.0-b65 mixed mode windows-x86 )
# Problematic frame:
# C [KERNELBASE.dll+0xc41f]
#
# Failed to write core dump. Minidumps are not enabled by default on client versions of Windows
#
# An error report file with more information is saved as:
# D:\work\authoring\authoringtool_test\SceneBuilder\app\hs_err_pid15884.log
#
# If you would like to submit a bug report, please visit:
# http://bugreport.sun.com/bugreport/crash.jsp
# The crash happened outside the Java Virtual Machine in native code.
# See problematic frame for where to report the bug.
#
Phoning home...
Using server: 10.161.186.18, port 4711