pretty: trivial style fix

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

pretty.c

@@ -497,7 +497,7 @@ void pp_user_info(struct pretty_print_context *pp,
 static int is_empty_line(const char *line, int *len_p)
 {
 	int len = *len_p;
-	while (len && isspace(line[len-1]))
+	while (len && isspace(line[len - 1]))
 		len--;
 	*len_p = len;
 	return !len;