enabling and disabling series in group freeze app

[Sanquira]

Related to issue 158

When the chart has multiple axis groups and all axes in one group are disabled program freezes.

Sample code:

public static void main(String[] args) throws Exception {
        double[] xData = new double[]{0.0, 1.0, 2.0};
        double[] yData = new double[]{2.0, 1.0, 0.0};
        XYChart chart = new XYChart(500, 200);
        XYSeries xySeries = chart.addSeries("Sample Chart", xData, yData);
        XYSeries xySeries2 = chart.addSeries("Sample Chart2", xData, yData);
        xySeries.setYAxisGroup(0);
        xySeries2.setYAxisGroup(1);
        xySeries.setEnabled(false);
        new SwingWrapper(chart).displayChart();
}

[timmolter]

Thanks for the report. I'll look into it soon.