Basefield fix

src/EPPlus/Table/PivotTable/Calculation/ShowDataAs/PivotShowAsPercentOfRunningTotal.cs

@@ -20,6 +20,10 @@ internal class PivotShowAsPercentOfRunningTotal : PivotShowAsRunningTotal
  internal override void Calculate(ExcelPivotTableDataField df, List<int> fieldIndex, ref PivotCalculationStore calculatedItems)
  {
  CalculateRunningTotal(df, fieldIndex, ref calculatedItems, true);
+ if (_bf < 0)
+ {
+ return;
+ }
  foreach (var key in calculatedItems.Index.OrderBy(x => x.Key, ArrayComparer.Instance))
  {
  if (IsSumBefore(key.Key, _bf, fieldIndex, _colFieldsStart))