java.lang.AssertionError
   at javafx.embed.swing.SwingDnD.getDragSource(SwingDnD.java:324)
   at javafx.embed.swing.SwingDnD.access$500(SwingDnD.java:71)
   at javafx.embed.swing.SwingDnD$DnDTransferable.isDataFlavorSupported(SwingDnD.java:476)
   at sun.awt.dnd.SunDropTargetContextPeer.isDataFlavorSupported(SunDropTargetContextPeer.java:208)
   at sun.awt.datatransfer.TransferableProxy.isDataFlavorSupported(TransferableProxy.java:68)
   at java.awt.dnd.DropTargetContext$TransferableProxy.isDataFlavorSupported(DropTargetContext.java:355)
   at org.openide.nodes.NodeTransfer.findPaste(NodeTransfer.java:302)
   at org.openide.nodes.AbstractNode.createPasteTypes(AbstractNode.java:527)
   at org.openide.nodes.AbstractNode.getDropType(AbstractNode.java:561)
   at org.openide.explorer.view.DragDropUtilities.getDropType(DragDropUtilities.java:314)
   at org.openide.explorer.view.TreeViewDropSupport.canDrop(TreeViewDropSupport.java:658)
   at org.openide.explorer.view.TreeViewDropSupport.doDragOver(TreeViewDropSupport.java:189)
   at org.openide.explorer.view.TreeViewDropSupport.dragOver(TreeViewDropSupport.java:153)
   at java.awt.dnd.DropTarget.dragOver(DropTarget.java:381)
   at sun.awt.dnd.SunDropTargetContextPeer.processMotionMessage(SunDropTargetContextPeer.java:474)
   at sun.awt.X11.XDropTargetContextPeer.processMotionMessage(XDropTargetContextPeer.java:178)
   at sun.awt.dnd.SunDropTargetContextPeer$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:4716)
   at java.awt.Container.dispatchEventImpl(Container.java:2287)
   at java.awt.Component.dispatchEvent(Component.java:4687)
   at java.awt.LightweightDispatcher.retargetMouseEvent(LightweightDispatcher.java:4832)
   at java.awt.LightweightDispatcher.processDropTargetEvent(LightweightDispatcher.java:4566)
   at java.awt.LightweightDispatcher.dispatchEvent(LightweightDispatcher.java:4417)
   at java.awt.Container.dispatchEventImpl(Container.java:2273)
   at java.awt.Window.dispatchEventImpl(Window.java:2719)
   at java.awt.Component.dispatchEvent(Component.java:4687)
   at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:723)
   at java.awt.EventQueue.access$200(EventQueue.java:103)
   at java.awt.EventQueue$3.run(EventQueue.java:682)
   at java.awt.EventQueue$3.run(EventQueue.java:680)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
   at java.awt.EventQueue$4.run(EventQueue.java:696)
   at java.awt.EventQueue$4.run(EventQueue.java:694)
   at java.security.AccessController.doPrivileged(AccessController.java:0)
   at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
   at java.awt.EventQueue.dispatchEvent(EventQueue.java:693)
   at org.netbeans.core.TimableEventQueue.dispatchEvent(TimableEventQueue.java:158)
   at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
   at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
   at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
   at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
   at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)