In my application series are added to a chart dynamically but the data of the series is updated ongoing.

If a series is changed which is not shown in a chart a NPE is thrown:
java.lang.NullPointerException
 at javafx.scene.chart.XYChart$Series$1.onChanged(XYChart.java:1507)
 at com.sun.javafx.collections.ListListenerHelper$SingleChange.fireValueChangedEvent(ListListenerHelper.java:158)
 at com.sun.javafx.collections.ListListenerHelper.fireValueChangedEvent(ListListenerHelper.java:72)
 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)

Reason: At line 1507 in XYChart the getChart() method is not null checked...