Tweaked the row height custom flag

row.go

@@ -1,14 +1,16 @@
 package xlsx
 
 type Row struct {
-	Cells  []*Cell
-	Hidden bool
-	Sheet  *Sheet
-	Height float64
+	Cells    []*Cell
+	Hidden   bool
+	Sheet    *Sheet
+	Height   float64
+	isCustom bool
 }
 
 func (r *Row) SetHeightCM(ht float64) {
 	r.Height = ht * 28.3464567 // Convert CM to postscript points
+	r.isCustom = true
 }
 
 func (r *Row) AddCell() *Cell {

sheet.go

@@ -110,7 +110,7 @@ func (s *Sheet) makeXLSXSheet(refTable *RefTable, styles *xlsxStyleSheet) *xlsxW
 		}
 		xRow := xlsxRow{}
 		xRow.R = r + 1
-		if row.Height > 0 {
+		if row.isCustom {
 			xRow.CustomHeight = true
 			xRow.Ht = fmt.Sprintf("%g", row.Height)
 		}