fix grand totals with empty fields

cell/model/PivotTables.js

@@ -2791,14 +2791,14 @@ CT_pivotTableDefinition.prototype.asc_set = function (api, newVal) {
 CT_pivotTableDefinition.prototype.asc_setRowGrandTotals = function(newVal) {
 	var res;
 	this.rowGrandTotals = newVal;
-	if (res = this.changeGrandTotals(this.rowItems, newVal)) {
+	if (this.rowFields && (res = this.changeGrandTotals(this.rowItems, newVal))) {
 		this.getRange().setOffsetLast(new AscCommonExcel.CRangeOffset(0, res));
 	}
 };
 CT_pivotTableDefinition.prototype.asc_setColGrandTotals = function(newVal) {
 	var res;
 	this.colGrandTotals = newVal;
-	if (res = this.changeGrandTotals(this.colItems, newVal)) {
+	if (this.colFields && (res = this.changeGrandTotals(this.colItems, newVal))) {
 		this.getRange().setOffsetLast(new AscCommonExcel.CRangeOffset(res, 0));
 	}
 };