check for notes before deleting them

autogen.go

@@ -13,9 +13,14 @@ import (
 // del     : true means empty out existing notes, otherwise append
 func (repo *Repo) AutogenSave(files []string, refname string, del bool) error {
 	if del {
-		cmd := []string{"git", "notes", "remove", refname}
+		cmd := []string{"git", "notes", "show", refname}
 		if err := repo.StrictRun(cmd); err != nil {
-			return err
+			// if there are not any notes, no need to remove them
+		} else {
+			cmd := []string{"git", "notes", "remove", refname}
+			if err := repo.StrictRun(cmd); err != nil {
+				return err
+			}
 		}
 	}
 	for _, fname := range files {