Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javafx.embed.swing.SwingDnD$2.dragDropEnd(SwingDnD.java:117)
at java.awt.dnd.DnDEventMulticaster.dragDropEnd(DnDEventMulticaster.java:111)
at java.awt.dnd.DragSource.processDragDropEnd(DragSource.java:769)
at java.awt.dnd.DragSourceContext.dragDropEnd(DragSourceContext.java:437)
at sun.awt.dnd.SunDragSourceContextPeer$EventDispatcher.run(SunDragSourceContextPeer.java:491)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:701)
at java.awt.EventQueue.access$000(EventQueue.java:102)
at java.awt.EventQueue$3.run(EventQueue.java:662)
at java.awt.EventQueue$3.run(EventQueue.java:660)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:671)
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)

It's happens on drop with any data formats and any transfer modes.