I've created a program for charts, and I get exception in the pointed string. But actually, no any one line of my code is mentioned in exception, and there is no obvious reason for this.

Code:

import java.util.Arrays;
import java.util.Comparator;
import java.util.Random;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.control.TextField;
import javafx.scene.layout.Pane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class JavaCharts extends Application {

    public static void main(String[] args) {
        launch(args);
    }
    NumberAxis axis1 = new NumberAxis(0, 100, 10);
    NumberAxis axis2 = new NumberAxis(0, 100, 10);
    LineChart testedLineChart = new LineChart(axis1, axis2);
    VBox vb = new VBox();

    @Override
    public void start(Stage stage) throws Exception {
        testedLineChart.setTitle("LineChart");
        testedLineChart.setStyle("-fx-border-color: darkgray;");

        ObservableList list = FXCollections.observableArrayList();
        int max = 100;
        int min = 30;

        for (int i = 0; i < 30; i++) {
            XYChart.Data newData = new XYChart.Data();
            newData.setXValue(new Random().nextDouble() * (max - min) + min);
            newData.setYValue(new Random().nextDouble() * (max - min) + min);
            list.add(newData);
        }
        Object[] array = list.toArray();
        Arrays.sort(array, new Comparator() {

            @Override
            public int compare(Object t, Object t1) {
                return (int) Math.round(((Double) ((XYChart.Data) t).getXValue()) - ((Double) ((XYChart.Data) t1).getXValue()));
            }
        });

        XYChart.Series serie = new XYChart.Series("serie", FXCollections.observableArrayList(array));

        testedLineChart.getData().add(serie);
        testedLineChart.setAlternativeColumnFillVisible(true);
        testedLineChart.setAlternativeRowFillVisible(true);

        Pane pane = new Pane();
        pane.setPrefSize(600, 600);

        TextField tf = new TextField("Text");

        //axis1.labelProperty().bindBidirectional(tf.textProperty());//Doesn't throw exception
        tf.textProperty().bindBidirectional(axis1.labelProperty());//Throw exception

        pane.setPrefSize(600, 600);
        pane.getChildren().add(testedLineChart);

        vb.getChildren().addAll(pane, tf);

        Scene scene = new Scene(vb, 700, 700);
        stage.setScene(scene);
        stage.show();
    }
}

To reproduce - type in any text.

Exception:
java.lang.NullPointerException
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.defaultKeyTyped(TextInputControlBehavior.java:219)
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callAction(TextInputControlBehavior.java:129)
at com.sun.javafx.scene.control.behavior.BehaviorBase.callActionForEvent(BehaviorBase.java:157)
at com.sun.javafx.scene.control.behavior.TextInputControlBehavior.callActionForEvent(TextInputControlBehavior.java:117)
at com.sun.javafx.scene.control.behavior.BehaviorBase$1.handle(BehaviorBase.java:121)
at com.sun.javafx.scene.control.behavior.BehaviorBase$1.handle(BehaviorBase.java:119)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:64)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Scene$KeyHandler.process(Scene.java:3478)
at javafx.scene.Scene$KeyHandler.access$2300(Scene.java:3433)
at javafx.scene.Scene.impl_processKeyEvent(Scene.java:1865)
at javafx.scene.Scene$ScenePeerListener.keyEvent(Scene.java:2231)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleKeyEvent(GlassViewEventHandler.java:126)
at com.sun.glass.ui.View.handleKeyEvent(View.java:518)
at com.sun.glass.ui.View.notifyKey(View.java:951)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:29)
at com.sun.glass.ui.win.WinApplication$2$1.run(WinApplication.java:62)
at java.lang.Thread.run(Thread.java:722)