py/persistentcode: Change "len" type to size_t for mp_obj_str_get_data.
@@ -560,7 +560,7 @@ STATIC void save_obj(mp_print_t *print, mp_obj_t o) {
} else {
obj_type = 'b';
}
- mp_uint_t len;
+ size_t len;
const char *str = mp_obj_str_get_data(o, &len);
mp_print_bytes(print, &obj_type, 1);
mp_print_uint(print, len);
