When doing drag and drop operation with Scene Builder 2.0, the assertion below is sometimes raised.
Drag and drop seems to be unaffected.

I've never seen this assertion before JDK 1.8.0-ea-b117.

Exception in thread "JavaFX Application Thread" java.lang.AssertionError
at com.sun.javafx.tk.quantum.QuantumClipboard.releaseCurrentDragboard(QuantumClipboard.java:161)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$6.run(GlassSceneDnDEventHandler.java:153)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$6.run(GlassSceneDnDEventHandler.java:145)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.handleDragEnd(GlassSceneDnDEventHandler.java:145)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleDragEnd(GlassViewEventHandler.java:615)
at com.sun.glass.ui.View.handleDragEnd(View.java:652)
at com.sun.glass.ui.View.notifyDragEnd(View.java:966)
at com.sun.glass.ui.mac.MacPasteboard._putItemsFromArray(Native Method)
at com.sun.glass.ui.mac.MacPasteboard.putItemsFromArray(MacPasteboard.java:143)
at com.sun.glass.ui.mac.MacPasteboard.putItems(MacPasteboard.java:165)
at com.sun.glass.ui.mac.MacSystemClipboard.pushToSystem(MacSystemClipboard.java:223)
at com.sun.glass.ui.SystemClipboard.flush(SystemClipboard.java:51)
at com.sun.glass.ui.ClipboardAssistance.flush(ClipboardAssistance.java:59)
at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:274)
at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1149)
at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2886)
at javafx.scene.Scene$DnDGesture.process(Scene.java:2947)
at javafx.scene.Scene$DnDGesture.access$8400(Scene.java:2842)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3680)
at javafx.scene.Scene$MouseHandler.access$1800(Scene.java:3389)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1651)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2442)
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)