Add missing error checks in `getSheetMap` to fix panic(#1437)

Unit tests updated

excelize.go

@@ -179,7 +179,9 @@ func OpenReader(r io.Reader, opts ...Options) (*File, error) {
 	if f.CalcChain, err = f.calcChainReader(); err != nil {
 		return f, err
 	}
-	f.sheetMap = f.getSheetMap()
+	if f.sheetMap, err = f.getSheetMap(); err != nil {
+		return f, err
+	}
 	if f.Styles, err = f.stylesReader(); err != nil {
 		return f, err
 	}

excelize_test.go

@@ -250,7 +250,10 @@ func TestOpenReader(t *testing.T) {
 		assert.NoError(t, zw.Close())
 		return buf
 	}
-	for _, defaultXMLPath := range []string{defaultXMLPathCalcChain, defaultXMLPathStyles} {
+	for _, defaultXMLPath := range []string{
+		defaultXMLPathCalcChain,
+		defaultXMLPathStyles,
+		defaultXMLPathWorkbookRels} {
 		_, err = OpenReader(preset(defaultXMLPath))
 		assert.EqualError(t, err, "XML syntax error on line 1: invalid UTF-8")
 	}

sheet.go

@@ -454,10 +454,16 @@ func (f *File) GetSheetList() (list []string) {
 
 // getSheetMap provides a function to get worksheet name and XML file path map
 // of the spreadsheet.
-func (f *File) getSheetMap() map[string]string {
+func (f *File) getSheetMap() (map[string]string, error) {
 	maps := map[string]string{}
-	wb, _ := f.workbookReader()
-	rels, _ := f.relsReader(f.getWorkbookRelsPath())
+	wb, err := f.workbookReader()
+	if err != nil {
+		return nil, err
+	}
+	rels, err := f.relsReader(f.getWorkbookRelsPath())
+	if err != nil {
+		return nil, err
+	}
 	for _, v := range wb.Sheets.Sheet {
 		for _, rel := range rels.Relationships {
 			if rel.ID == v.ID {
@@ -471,7 +477,7 @@ func (f *File) getSheetMap() map[string]string {
 			}
 		}
 	}
-	return maps
+	return maps, nil
 }
 
 // getSheetXMLPath provides a function to get XML file path by given sheet

sheet_test.go

@@ -378,6 +378,12 @@ func TestGetSheetMap(t *testing.T) {
 	}
 	assert.Equal(t, len(sheetMap), 2)
 	assert.NoError(t, f.Close())
+
+	f = NewFile()
+	f.WorkBook = nil
+	f.Pkg.Store(defaultXMLPathWorkbook, MacintoshCyrillicCharset)
+	_, err = f.getSheetMap()
+	assert.EqualError(t, err, "XML syntax error on line 1: invalid UTF-8")
 }
 
 func TestSetActiveSheet(t *testing.T) {