[fix] workaround for gcc optimizer bug in Tree::to_arena(csubstr)
[fix] workaround for gcc optimizer bug in Tree::to_arena(csubstr)

see https://github.com/biojppm/rapidyaml/pull/264#issuecomment-1262133637

biojppm/rapidyaml,biojppm/rapidyaml,biojppm/rapidyaml