java.lang.StringIndexOutOfBoundsException: String index out of range: -2
  at java.lang.String.substring(String.java:1931)
  at org.jabref.logic.importer.fileformat.PdfContentImporter.importDatabase(PdfContentImporter.java:372)
  at org.jabref.logic.externalfiles.ExternalFilesContentImporter.importPDFContent(ExternalFilesContentImporter.java:24)
  at org.jabref.gui.externalfiles.ImportHandler.importAsNewEntries(ImportHandler.java:72)
  at org.jabref.gui.externalfiles.FindUnlinkedFilesDialog.startImport(FindUnlinkedFilesDialog.java:332)
  at org.jabref.gui.externalfiles.FindUnlinkedFilesDialog.lambda$initialize$942(FindUnlinkedFilesDialog.java:195)
  at javafx.scene.control.Dialog.impl_setResultAndClose(Dialog.java:1026)
  at javafx.scene.control.DialogPane.lambda$createButton$3(DialogPane.java:777)
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
  at javafx.event.Event.fireEvent(Event.java:198)
  at javafx.scene.Node.fireEvent(Node.java:8413)
  at javafx.scene.control.Button.fire(Button.java:185)
  at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
  at javafx.event.Event.fireEvent(Event.java:198)
  at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
  at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
  at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
  at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
  at java.security.AccessController.doPrivileged(Native Method)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:432)
  at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
  at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
  at com.sun.glass.ui.View.notifyMouse(View.java:937)
  at com.sun.glass.ui.gtk.GtkApplication.enterNestedEventLoopImpl(Native Method)
  at com.sun.glass.ui.gtk.GtkApplication._enterNestedEventLoop(GtkApplication.java:211)
  at com.sun.glass.ui.Application.enterNestedEventLoop(Application.java:511)
  at com.sun.glass.ui.EventLoop.enter(EventLoop.java:107)
  at com.sun.javafx.tk.quantum.QuantumToolkit.enterNestedEventLoop(QuantumToolkit.java:590)
  at javafx.stage.Stage.showAndWait(Stage.java:474)
  at javafx.scene.control.HeavyweightDialog.showAndWait(HeavyweightDialog.java:162)
  at javafx.scene.control.Dialog.showAndWait(Dialog.java:341)
  at org.jabref.gui.externalfiles.FindUnlinkedFilesAction.execute(FindUnlinkedFilesAction.java:26)
  at org.jabref.gui.actions.JabRefAction.lambda$new$1218(JabRefAction.java:29)
  at org.controlsfx.control.action.Action.handle(Action.java:419)
  at org.controlsfx.control.action.Action.handle(Action.java:64)
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
  at javafx.event.Event.fireEvent(Event.java:198)
  at javafx.scene.control.MenuItem.fire(MenuItem.java:462)
  at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.doSelect(ContextMenuContent.java:1405)
  at com.sun.javafx.scene.control.skin.ContextMenuContent$MenuItemContainer.lambda$createChildren$6(ContextMenuContent.java:1358)
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
  at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
  at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
  at javafx.event.Event.fireEvent(Event.java:198)
  at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
  at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
  at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
  at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
  at java.security.AccessController.doPrivileged(Native Method)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$2(GlassViewEventHandler.java:432)
  at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
  at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
  at com.sun.glass.ui.View.notifyMouse(View.java:937)
  at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
  at com.sun.glass.ui.gtk.GtkApplication.lambda$null$5(GtkApplication.java:139)
  at java.lang.Thread.run(Thread.java:748)