SeriesLine: allowSliding make PointLabel, which must be hidden, shown outsize of view port

[phong010198]

PointLabels are shown outsize of view port like 2 screenshots bellow.

  DChartComboO(
    allowSliding: true, // allow scrolling
    configSeriesLine: const ConfigSeriesLineO(
      seriesColor: AppColors.red200,
      includePointLabel: true,
      pointLabelDecorator: PointLabelDecoratorO(
        labelStyle: LabelStyle(),
        verticalPadding: 14,
        horizontalPadding: 6,
      ),
      includePoints: true,
      pointRadiusBase: 3,
    ),
  )