[fixed] empty value is^W was returned if cell is string formula

col.go

@@ -54,10 +54,10 @@ func (xf *XfRk) String(wb *WorkBook) string {
 		fNo := wb.Xfs[idx].formatNo()
 		if fNo >= 164 { // user defined format
 			if formatter := wb.Formats[fNo]; formatter != nil {
-				if (strings.Contains(formatter.str, "#") || strings.Contains(formatter.str, ".00")){
+				if strings.Contains(formatter.str, "#") || strings.Contains(formatter.str, ".00") {
 					//If format contains # or .00 then this is a number
-					return xf.Rk.String()					
-				}else{
+					return xf.Rk.String()
+				} else {
 					i, f, isFloat := xf.Rk.number()
 					if !isFloat {
 						f = float64(i)
@@ -165,6 +165,18 @@ func (c *NumberCol) String(wb *WorkBook) []string {
 	return []string{strconv.FormatFloat(c.Float, 'f', -1, 64)}
 }
 
+type FormulaStringCol struct {
+	Col
+	RenderedValue string
+}
+
+func (c *FormulaStringCol) String(wb *WorkBook) []string {
+	return []string{c.RenderedValue}
+}
+
+//str, err = wb.get_string(buf_item, size)
+//wb.sst[offset_pre] = wb.sst[offset_pre] + str
+
 type FormulaCol struct {
 	Header struct {
 		Col