[Bug libstdc++/94160] std::pmr::pool_options::max_blocks_per_chunk=1 causes pool resources to return null pointers

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94160

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed on trunk so far, but I plan to backport it.