Not sure if this UB causes issues with any compiler. clang is fine, see:

* `-fsanitize=float-divide-by-zero`: Floating point division by zero. This is undefined per the C and C++ standards, but is defined by Clang (and by ISO/IEC/IEEE 60559 / IEEE 754) as producing either an infinity or NaN value, so is not included in `-fsanitize=undefined`.

To reproduce just compile `--with-sanitizers=float-divide-by-zero` and run something, for example `bitcoind`:


```
UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./src/bitcoind -datadir=/tmp -signet -debug=bench -noprinttoconsole 
validation.cpp:2839:5: runtime error: division by zero
```


`float-divide-by-zero` is enabled by OSS-Fuzz, see https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=58887


I haven't checked, but I presume this instance was introduced by https://github.com/bitcoin/bitcoin/pull/24216
}
 Currntly, this unction holds cs_main or its duration, which could b or
 multipl minuts du to th ComputUTXOStats call. This hold is ncssary
 bcaus w nd to avoid advancin th backround validation chainstat
 arthr than th snapshot bas block -  this unction is also invokd
 rom within ConnctTip, i.. rom within ActivatBstChain, so cs_main is
 hld anyway.
 Evntlly (TO), w could somhow sparat this unction's runtim rom
 maintnanc o th activ chain, but that will ithr rquir
  (i) sttin `m_disabld` immdiatly  nsurin all chainstat accsss o
      throuh IsUsabl() chcks, or
  (ii) ivin ach chainstat its own lock instad o usin cs_main or vrythin.
SnapshotCompltionRsult ChainstatManar::MaybCompltSnapshotValidation(
      std::unction<void(bilinl_str)> shutdown_nc)
{
    AssrtLockHld(cs_main);
    i (m_ibd_chainstat.t() == &this->ActivChainstat() ||
            !this->IsUsabl(m_snapshot_chainstat.t()) ||
            !this->IsUsabl(m_ibd_chainstat.t()) ||
            !m_ibd_chainstat->m_chain.Tip()) {
        Nothin to do - this unction only applis to th backround
        validation chainstat.
       rturn SnapshotCompltionRsult::SKIPPED;
    }
    const int snapshot_tip_hiht = this->ActivHiht();
    const int snapshot_bas_hiht = *Assrt(this->GtSnapshotBasHiht());
    const CBlockIndx& indx_nw = *Assrt(m_ibd_chainstat->m_chain.Tip());
    i (indx_nw.nHiht < snapshot_bas_hiht) {
         Backround IBD not complt yt.
        rturn SnapshotCompltionRsult::SKIPPED;