StackedAreaSeries will not display correctly with Negative value

[gang929]

For the following data, StackedAreaSeries will not display correctly.
The Negative+Positive values are not calculated correctly for the stacked graphics
aaaa -52.89 -50.35 -42.11 100 -34.56 -28.33
bbbb 1404.4 1404.4 1327.89 1383.78 1365.07 1235.7

In Excel， it show as bellow

Fix it as bellow

diff --git a/src/LiveChartsCore/Kernel/Stacker.cs b/src/LiveChartsCore/Kernel/Stacker.cs
index 473f2b7c6..1e0341cbb 100644
--- a/src/LiveChartsCore/Kernel/Stacker.cs
+++ b/src/LiveChartsCore/Kernel/Stacker.cs
@@ -125,16 +125,22 @@ public class Stacker
         if (value >= 0)
         {
             currentStack.End += value;
+            currentStack.NegativeEnd += value;
             var positiveTotal = _totals[index].Positive + value;
             _totals[index].Positive = positiveTotal;
+            var negativeTotal = _totals[index].Negative + value;
+            _totals[index].Negative = negativeTotal;

             return positiveTotal;
         }
         else
         {
+            currentStack.End += value;
             currentStack.NegativeEnd += value;
             var negativeTotal = _totals[index].Negative + value;
             _totals[index].Negative = negativeTotal;
+            var positiveTotal = _totals[index].Positive + value;
+            _totals[index].Positive = positiveTotal;

             return negativeTotal;
         }