This fix formula calculation accuracy issue and panic when set pane

- Fix `GROWTH` and `TREND` calculation accuracy issue
- Fix panic when add pane on empty sheet views worksheet
- New exported constants `MinFontSize`

1 files changed, 1 insertions, 1 deletions

diff --git a/styles.go b/styles.go
index 4b5c772..f8f4030 100644
--- a/styles.go
+++ b/styles.go
@@ -2042,7 +2042,7 @@ func (f *File) getFontID(styleSheet *xlsxStyleSheet, style *Style) (fontID int)
 // settings.
 func (f *File) newFont(style *Style) *xlsxFont {
 	fontUnderlineType := map[string]string{"single": "single", "double": "double"}
-	if style.Font.Size < 1 {
+	if style.Font.Size < MinFontSize {
 		style.Font.Size = 11
 	}
 	if style.Font.Color == "" {