This fixes an intermittent seg fault when `GC.compact` is used.

Relates to https://gitlab.com/gitlab-com/gl-infra/production/-/issues/3370

CHANGELOG.md: https://github.com/k0kubun/hamlit/blob/master/CHANGELOG.md
Diff: https://github.com/k0kubun/hamlit/compare/v2.11.1..v2.14.2