Reset preferences throws not on FX Thread exception multiple times

[Siedlerchr]

current master (2019-01-28)

To FIX: Replace the Swing Worker with a Background Task.

	at org.jabref.gui.preferences.PreviewPrefsTab$1.done(PreviewPrefsTab.java:239)
	at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
	at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
	at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
	at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)

java.lang.IllegalStateException: Not on FX application thread; currentThread = AWT-EventQueue-0
	at com.sun.javafx.tk.Toolkit.checkFxUserThread(Toolkit.java:279)
	at com.sun.javafx.tk.quantum.QuantumToolkit.checkFxUserThread(QuantumToolkit.java:423)
	at javafx.scene.Parent$2.onProposedChange(Parent.java:367)
	at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:113)
	at com.sun.javafx.collections.VetoableListDecorator.setAll(VetoableListDecorator.java:108)
	at com.sun.javafx.scene.control.skin.LabeledSkinBase.updateChildren(LabeledSkinBase.java:575)
	at com.sun.javafx.scene.control.skin.LabeledSkinBase.handleControlPropertyChanged(LabeledSkinBase.java:204)
	at com.sun.javafx.scene.control.skin.ListCellSkin.handleControlPropertyChanged(ListCellSkin.java:49)
	at com.sun.javafx.scene.control.skin.BehaviorSkinBase.lambda$registerChangeListener$61(BehaviorSkinBase.java:197)
	at com.sun.javafx.scene.control.MultiplePropertyChangeListenerHandler$1.changed(MultiplePropertyChangeListenerHandler.java:55)
	at javafx.beans.value.WeakChangeListener.changed(WeakChangeListener.java:89)
	at com.sun.javafx.binding.ExpressionHelper$SingleChange.fireValueChangedEvent(ExpressionHelper.java:182)
	at com.sun.javafx.binding.ExpressionHelper.fireValueChangedEvent(ExpressionHelper.java:81)
	at javafx.beans.property.StringPropertyBase.fireValueChangedEvent(StringPropertyBase.java:103)
	at javafx.beans.property.StringPropertyBase.markInvalid(StringPropertyBase.java:110)
	at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:144)
	at javafx.beans.property.StringPropertyBase.set(StringPropertyBase.java:49)
	at javafx.beans.property.StringProperty.setValue(StringProperty.java:65)
	at javafx.scene.control.Labeled.setText(Labeled.java:145)
	at com.sun.javafx.scene.control.skin.ListViewSkin$2.updateItem(ListViewSkin.java:319)
	at javafx.scene.control.ListCell.updateItem(ListCell.java:471)
	at javafx.scene.control.ListCell.lambda$new$160(ListCell.java:167)
	at javafx.collections.WeakListChangeListener.onChanged(WeakListChangeListener.java:88)
	at com.sun.javafx.collections.ListListenerHelper$Generic.fireValueChangedEvent(ListListenerHelper.java:329)
	at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:73)
	at javafx.collections.ObservableListBase.fireChange(ObservableListBase.java:233)
	at javafx.collections.ListChangeBuilder.commit(ListChangeBuilder.java:482)
	at javafx.collections.ListChangeBuilder.endChange(ListChangeBuilder.java:541)
	at javafx.collections.ObservableListBase.endChange(ObservableListBase.java:205)
	at javafx.collections.ModifiableObservableListBase.add(ModifiableObservableListBase.java:155)
	at java.util.AbstractList.add(AbstractList.java:108)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.ArrayList.forEach(ArrayList.java:1257)
	at java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:390)
	at java.util.stream.Sink$ChainedReference.end(Sink.java:258)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at org.jabref.gui.preferences.PreviewPrefsTab$1.done(PreviewPrefsTab.java:239)
	at javax.swing.SwingWorker$5.run(SwingWorker.java:737)
	at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.run(SwingWorker.java:832)
	at sun.swing.AccumulativeRunnable.run(AccumulativeRunnable.java:112)
	at javax.swing.SwingWorker$DoSubmitAccumulativeRunnable.actionPerformed(SwingWorker.java:842)
	at javax.swing.Timer.fireActionPerformed(Timer.java:313)
	at javax.swing.Timer$DoPostEvent.run(Timer.java:245)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
	at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
	at java.awt.EventQueue.access$500(EventQueue.java:97)
	at java.awt.EventQueue$3.run(EventQueue.java:709)
	at java.awt.EventQueue$3.run(EventQueue.java:703)
	at java.security.AccessController.doPrivileged(Native Method)
	at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
	at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
	at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
	at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)