java.lang.NullPointerException: Cannot read field "dragboard" because "this.this$0.dndGesture" is null
  at org.jabref.merged.module@5.2.214/javafx.scene.Scene$DropTargetListener.drop(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.lambda$handleDragDrop$2(Unknown Source)
  at java.base/java.security.AccessController.doPrivileged(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.handleDragDrop(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleDragDrop$11(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.javafx.tk.quantum.GlassViewEventHandler.handleDragDrop(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.glass.ui.View.handleDragDrop(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.glass.ui.View.notifyDragDrop(Unknown Source)
  at org.jabref.merged.module@5.2.214/com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
  at org.jabref.merged.module@5.2.214/com.sun.glass.ui.gtk.GtkApplication.lambda$runLoop$11(Unknown Source)
  at java.base/java.lang.Thread.run(Unknown Source)