Handle empty mailqueue gracefully, it is not an error

parser/parser.go

@@ -52,7 +52,7 @@ func ParseMailQ(dataSource io.Reader) ([]QEntry, error) {
     line = scanner.Text()
     if strings.HasPrefix(line, "Mail queue is empty") {
 		// If mail queue is empty, there is nothing to do
-		return nil, errors.New(line)
+		return []QEntry{}, nil
 	} else if strings.HasPrefix(line, "-Queue ID-") == false {
 		// Abort if input does not look like output from mailq(1)
 		return nil, errors.New("Sorry, this does not look like output from mailq(1).")