Simplify code and update unit test

Improve unit test coverage for the functions: `NewStyle`, `SetActiveSheet`, `SearchSheet` and `deleteAndAdjustDefinedNames`
Simplify code and add comments for the function: `deleteAndAdjustDefinedNames`

1 files changed, 3 insertions, 6 deletions

diff --git a/sheet.go b/sheet.go
index 6244e02..99ae1a2 100644
--- a/sheet.go
+++ b/sheet.go
@@ -586,15 +586,12 @@ func (f *File) DeleteSheet(name string) {
 	f.SetActiveSheet(f.GetSheetIndex(activeSheetName))
 }
 
+// deleteAndAdjustDefinedNames delete and adjust defined name in the workbook
+// by given worksheet ID.
 func deleteAndAdjustDefinedNames(wb *xlsxWorkbook, deleteLocalSheetID int) {
-	if wb == nil {
+	if wb == nil || wb.DefinedNames == nil {
 		return
 	}
-
-	if wb.DefinedNames == nil {
-		return
-	}
-
 	for idx := 0; idx < len(wb.DefinedNames.DefinedName); idx++ {
 		dn := wb.DefinedNames.DefinedName[idx]
 		if dn.LocalSheetID != nil {