Do not double close reader (#29354) (#29370)

Backport #29354 by @KN4CK3R

Fixes #29346

Co-authored-by: KN4CK3R <admin@oldschoolhack.me>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/git/blob_nogogit.go

 
 // Close implements io.Closer
 func (b *blobReader) Close() error {
+	if b.rd == nil {
+		return nil
+	}
+
 	defer b.cancel()
 
-	return DiscardFull(b.rd, b.n+1)
+	if err := DiscardFull(b.rd, b.n+1); err != nil {
+		return err
+	}
+
+	b.rd = nil
+
+	return nil
 }

routers/web/repo/editor.go

 		}
 
 		d, _ := io.ReadAll(dataRc)
-		if err := dataRc.Close(); err != nil {
-			log.Error("Error whilst closing blob data: %v", err)
-		}
 
 		buf = append(buf, d...)
 		if content, err := charset.ToUTF8(buf, charset.ConvertOpts{KeepBOM: true}); err != nil {