This close #1963, prevent the GetStyle function panic when theme without sysClr

styles.go

@@ -1376,22 +1376,33 @@ var (
 	}
 )
 
+// colorChoice returns a hex color code from the actual color values.
+func (clr *decodeCTColor) colorChoice() *string {
+	if clr.SrgbClr != nil {
+		return clr.SrgbClr.Val
+	}
+	if clr.SysClr != nil {
+		return &clr.SysClr.LastClr
+	}
+	return nil
+}
+
 // GetBaseColor returns the preferred hex color code by giving hex color code,
 // indexed color, and theme color.
 func (f *File) GetBaseColor(hexColor string, indexedColor int, themeColor *int) string {
 	if f.Theme != nil && themeColor != nil {
 		clrScheme := f.Theme.ThemeElements.ClrScheme
 		if val, ok := map[int]*string{
-			0: &clrScheme.Lt1.SysClr.LastClr,
-			1: &clrScheme.Dk1.SysClr.LastClr,
-			2: clrScheme.Lt2.SrgbClr.Val,
-			3: clrScheme.Dk2.SrgbClr.Val,
-			4: clrScheme.Accent1.SrgbClr.Val,
-			5: clrScheme.Accent2.SrgbClr.Val,
-			6: clrScheme.Accent3.SrgbClr.Val,
-			7: clrScheme.Accent4.SrgbClr.Val,
-			8: clrScheme.Accent5.SrgbClr.Val,
-			9: clrScheme.Accent6.SrgbClr.Val,
+			0: clrScheme.Lt1.colorChoice(),
+			1: clrScheme.Dk1.colorChoice(),
+			2: clrScheme.Lt2.colorChoice(),
+			3: clrScheme.Dk2.colorChoice(),
+			4: clrScheme.Accent1.colorChoice(),
+			5: clrScheme.Accent2.colorChoice(),
+			6: clrScheme.Accent3.colorChoice(),
+			7: clrScheme.Accent4.colorChoice(),
+			8: clrScheme.Accent5.colorChoice(),
+			9: clrScheme.Accent6.colorChoice(),
 		}[*themeColor]; ok && val != nil {
 			return *val
 		}

styles_test.go

@@ -613,6 +613,8 @@ func TestGetThemeColor(t *testing.T) {
 	assert.Equal(t, "FFFFFF", f.getThemeColor(&xlsxColor{RGB: "FFFFFF"}))
 	assert.Equal(t, "FF8080", f.getThemeColor(&xlsxColor{Indexed: 2, Tint: 0.5}))
 	assert.Empty(t, f.getThemeColor(&xlsxColor{Indexed: len(IndexedColorMapping), Tint: 0.5}))
+	clr := &decodeCTColor{}
+	assert.Nil(t, clr.colorChoice())
 }
 
 func TestGetStyle(t *testing.T) {