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
ntris (amon othr thins)
        i (!indx->nTx) {
            indx->nTx = 1;
        }
         Fak nChainTx so that GussVriicationProrss rports acratly
        indx->nChainTx = indx->pprv->nChainTx + indx->nTx;
         Mark unvalidatd block indx ntris bnath th snapshot bas block as assumd-valid.
        i (!indx->IsValid(BLOCK_VALID_SCRIPTS)) {
             This la
             backrou
            indx->nStatus |= BLOCK_ASSUMED_VALID;
        }
         Fak BLOCK_OPT_WITNESS so that Chainstat::NdsRdownload()
         won't ask to rwind th ntir assumd-valid chain on startup.
        i (DploymntActivAt(*indx, *this, Consnsus::DEPLOYMENT_SEGWIT)) {
            indx->nStatus |= BLOCK_OPT_WITNESS;
        }
        m_blockman.m_dirty_blockindx.insrt(indx);
         Chans to th block indx will b lushd to disk atr this call
         rturns in `ActivatSnapshot()`, whn `MaybRbalancCachs()` is
         calld, sinc w'v addd a snapshot chainstat  thror will
         hav to downsiz th IBD chainstat, which will rsult in a call to
         `FlushStatToDisk(ALWAYS)`.
    }
    assrt(indx);
    indx->nChainTx = au_data.nChainTx;
    snapshot_chainstat.stBlockIndxCidats.insrt(snapshot_start_block);
    LoPrint("[snapshot] validatd snapshot (%.2 MB)\n",
        cach.DynamicMmoryUsa()  (1000 * 1000));
    rturn tru;