Dragging from Swing to JavaFX (JFXPanel) that was working in JavaFX 2.2 fails in JavaFX 8.0

MY application has a JFXPanel and a JTree. I support dragging items from the JTree and dropping them into my Scene. It is working on Java 7u17 with JavaFX 2.2.7, but when I run the same code on Java 8.0-b81 (JavaFX 8-b81) I get the following exceptions:

Exception in runnable
java.lang.AssertionError
at com.sun.javafx.tk.quantum.EmbeddedSceneDnD.createDragboard(EmbeddedSceneDnD.java:119)
at com.sun.javafx.tk.quantum.EmbeddedScene.createDragboard(EmbeddedScene.java:100)
at javafx.scene.input.Dragboard.impl_createDragboard(Dragboard.java:66)
at javafx.scene.Scene$DropTargetListener.dragEnter(Scene.java:2655)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$1.run(GlassSceneDnDEventHandler.java:55)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$1.run(GlassSceneDnDEventHandler.java:51)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.handleDragEnter(GlassSceneDnDEventHandler.java:51)
at com.sun.javafx.tk.quantum.EmbeddedSceneDropTarget$1.call(EmbeddedSceneDropTarget.java:88)
at com.sun.javafx.tk.quantum.EmbeddedSceneDropTarget$1.call(EmbeddedSceneDropTarget.java:77)
at com.sun.javafx.tk.quantum.AbstractEventLoop$CallableTask.doRun(AbstractEventLoop.java:66)
at com.sun.javafx.tk.quantum.AbstractEventLoop$Task.run(AbstractEventLoop.java:40)
at com.sun.javafx.application.PlatformImpl$5$1.run(PlatformImpl.java:223)
at com.sun.javafx.application.PlatformImpl$5$1.run(PlatformImpl.java:220)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl$5.run(PlatformImpl.java:220)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:94)
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$3$1.run(WinApplication.java:101)
at java.lang.Thread.run(Thread.java:722)
java.lang.RuntimeException: java.lang.RuntimeException: dndGesture.dragboard is null in dragOver
at com.sun.javafx.tk.quantum.AbstractEventLoop$CallableTask.getResult(AbstractEventLoop.java:76)
at com.sun.javafx.tk.quantum.AbstractEventLoop.send(AbstractEventLoop.java:105)
at com.sun.javafx.tk.quantum.FxEventLoop$Impl.send(FxEventLoop.java:60)
at com.sun.javafx.tk.quantum.FxEventLoop.sendEvent(FxEventLoop.java:130)
at com.sun.javafx.tk.quantum.EmbeddedSceneDropTarget.handleDragOver(EmbeddedSceneDropTarget.java:139)
at javafx.embed.swing.SwingDnD$3.dragOver(SwingDnD.java:190)
at java.awt.dnd.DropTarget.dragOver(DropTarget.java:381)
at sun.awt.dnd.SunDropTargetContextPeer.processMotionMessage(SunDropTargetContextPeer.java:474)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchMotionEvent(SunDropTargetContextPeer.java:823)
at sun.awt.dnd.SunDropTargetContextPeer$EventDispatcher.dispatchEvent(SunDropTargetContextPeer.java:769)
at sun.awt.dnd.SunDropTargetEvent.dispatch(SunDropTargetEvent.java:48)
at java.awt.Component.dispatchEventImpl(Component.java:4724)
at java.awt.Container.dispatchEventImpl(Container.java:2287)
at java.awt.Component.dispatchEvent(Component.java:4691)
at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4856)
at java.awt.LightweightDispatcher.processDropTargetEvent(Container.java:4590)
at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4441)
at java.awt.Container.dispatchEventImpl(Container.java:2273)
at java.awt.Window.dispatchEventImpl(Window.java:2721)
at java.awt.Component.dispatchEvent(Component.java:4691)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:722)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:681)
at java.awt.EventQueue$3.run(EventQueue.java:679)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.awt.EventQueue$4.run(EventQueue.java:695)
at java.awt.EventQueue$4.run(EventQueue.java:693)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:75)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:692)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:216)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:135)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:123)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:119)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:111)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)