Axis Breaks When Chart Has Null Data

[c0nstexpr]

Similar to #1294
I edit the view model implementation of Axes/Shared example in the project.

• Replace data type from int to TimeSpanPoint (or any other class type)
• Delete Values property assign for both series, only null collection
• Start the app, zoom out any chart then we got NaN on X axis

ViewModel.cs

using SkiaSharp;
using LiveChartsCore;
using LiveChartsCore.SkiaSharpView;
using LiveChartsCore.SkiaSharpView.Painting;
using LiveChartsCore.Drawing;
using LiveChartsCore.Measure;
using LiveChartsCore.Defaults;

public class ViewModel
{
    public ISeries[] SeriesCollection1 { get; set; }
    public ISeries[] SeriesCollection2 { get; set; }
    public Axis[] X1 { get; set; }
    public Axis[] X2 { get; set; }
    public Margin DrawMargin { get; set; }

    public ViewModel()
    {
        SeriesCollection1 = new ISeries[] { new LineSeries<TimeSpanPoint> {  } };
        SeriesCollection2 = new ISeries[] { new ColumnSeries<TimeSpanPoint> {  } };

        // ideally, when sharing an axis, you should set the // mark
        // initial limits for all the axes involved. // mark
        var padding = 3;
        var start = 0 - padding;
        // var end = values1.Length - 1 + padding;

        X1 = new Axis[]
        {
            new Axis
            {
                MinLimit = 1,
                MaxLimit = 2,
                CrosshairLabelsBackground = SKColors.OrangeRed.AsLvcColor(),
                CrosshairLabelsPaint = new SolidColorPaint(SKColors.White),
                CrosshairPaint = new SolidColorPaint(SKColors.OrangeRed.WithAlpha(50), 4),
                CrosshairPadding = new Padding(8),
                Labeler = value => value.ToString("N2")
            }
        };

        X2 = new Axis[]
        {
            new Axis
            {
                MinLimit = 1,
                MaxLimit = 2,
                CrosshairPaint = new SolidColorPaint(SKColors.OrangeRed.WithAlpha(50), 4)
            }
        };

        SharedAxes.Set(X1[0], X2[0]);

        // Force the chart to use 70px margin on the left, this way we can align both charts Y axes. // mark
        DrawMargin = new Margin(70, Margin.Auto, Margin.Auto, Margin.Auto);
    }        
}

[c0nstexpr]

I test several times, the problem also happens when the Value prop of TimeSpanPoint in both series has null value.

SeriesCollection1 = new ISeries[]
{
    new LineSeries<TimeSpanPoint>
    {
        Values = new TimeSpanPoint[] 
        {
            new TimeSpanPoint() { TimeSpan = TimeSpan.Zero, Value = null },
        }
    }
};
SeriesCollection2 = new ISeries[]
 {
    new LineSeries<TimeSpanPoint>
    {
        Values = new TimeSpanPoint[]
        {
            new TimeSpanPoint() { TimeSpan = TimeSpan.Zero, Value = null },
        }
    }
};

[beto-rodriguez]

Thanks for the report, this is fixed with the referenced commit and will be included in the next release of the library.