Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
        at javafx.embed.swing.SwingDnD$2.dragDropEnd(SwingDnD.java:119)
        at java.awt.dnd.DnDEventMulticaster.dragDropEnd(DnDEventMulticaster.java:110)
        at java.awt.dnd.DragSource.processDragDropEnd(DragSource.java:769)
        at java.awt.dnd.DragSourceContext.dragDropEnd(DragSourceContext.java:437)
        at sun.awt.dnd.SunDragSourceContextPeer$EventDispatcher.run(SunDragSourceContextPeer.java:491)
        at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
        at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:711)
        at java.awt.EventQueue.access$000(EventQueue.java:104)
        at java.awt.EventQueue$3.run(EventQueue.java:672)
        at java.awt.EventQueue$3.run(EventQueue.java:670)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
        at java.awt.EventQueue.dispatchEvent(EventQueue.java:681)
        at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
        at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
        at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
        at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
        at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)
Exception in runnable
java.lang.IllegalArgumentException: Key already associated with a running event loop: java.lang.Object@37e02b65
        at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:514)
        at com.sun.javafx.tk.quantum.FxEventLoop$Impl.start(FxEventLoop.java:49)
        at com.sun.javafx.tk.quantum.FxEventLoop.enterNestedLoop(FxEventLoop.java:96)
        at com.sun.javafx.tk.quantum.EmbeddedSceneDnD$ClipboardAssistanceImpl.flush(EmbeddedSceneDnD.java:167)
        at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:196)
        at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1189)
        at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2648)
        at javafx.scene.Scene$DnDGesture.process(Scene.java:2709)
        at javafx.scene.Scene$DnDGesture.access$8700(Scene.java:2603)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3340)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3164)
        at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3119)
        at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1559)
        at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2261)
        at com.sun.javafx.tk.quantum.EmbeddedScene$2.run(EmbeddedScene.java:184)
        at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:173)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:76)
        at com.sun.glass.ui.gtk.GtkApplication.enterNestedEventLoopImpl(Native Method)
        at com.sun.glass.ui.gtk.GtkApplication._enterNestedEventLoop(GtkApplication.java:137)
        at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:388)
        at com.sun.glass.ui.EventLoop.enter(EventLoop.java:83)
        at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:520)
        at com.sun.javafx.tk.quantum.FxEventLoop$Impl.start(FxEventLoop.java:49)
        at com.sun.javafx.tk.quantum.FxEventLoop.enterNestedLoop(FxEventLoop.java:96)
        at com.sun.javafx.tk.quantum.EmbeddedSceneDnD$ClipboardAssistanceImpl.flush(EmbeddedSceneDnD.java:167)
        at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:196)
        at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1189)
        at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2648)
        at javafx.scene.Scene$DnDGesture.process(Scene.java:2709)
        at javafx.scene.Scene$DnDGesture.access$8700(Scene.java:2603)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3340)
        at javafx.scene.Scene$MouseHandler.process(Scene.java:3164)
        at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3119)
        at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1559)
        at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2261)
        at com.sun.javafx.tk.quantum.EmbeddedScene$2.run(EmbeddedScene.java:184)
        at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:173)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:76)
        at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
        at com.sun.glass.ui.gtk.GtkApplication$3$1.run(GtkApplication.java:82)
        at java.lang.Thread.run(Thread.java:722)