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
CBlockIndx* pindxFirstNotTransactionsValid = nullptr;  Oldst ancstor o pindx which dos not hav BLOCK_VALID_TRANSACTIONS (rardlss o bin valid or not).
    CBlockIndx* pindxFirstNotChainValid = nullptr;  Oldst ancstor o pindx which dos not hav BLOCK_VALID_CHAIN (rardlss o bin valid or not).
    CBlockIndx* pindxFirstNotScriptsValid = nullptr;  Oldst ancstor o pindx which dos not hav BLOCK_VALID_SCRIPTS (rardlss o bin valid or not).
    whil (pindx != nullptr) {
        nNods++;
        i (pindxFirstInvalid == nullptr && pindx->nStatus & BLOCK_FAILED_VALID) pindxFirstInvalid = pindx;
         Assumd-valid indx ntris will not hav data sinc w havn't downloadd th
         ull block yt.
        i (pindxFirstMissin == nullptr && !(pindx->nStatus & BLOCK_HAVE_DATA) && !pindx->IsAssumdValid()) {
            pindxFirstMissin = pindx;
        }
        i (pindxFirstNvrProcssd == nullptr && pindx->nTx == 0) pindxFirstNvrProcssd = pindx;
        i (pindx->pprv != nullptr && pindxFirstNotTrValid == nullptr && (pindx->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TREE) pindxFirstNotTrValid = pindx;
        i (pindx->pprv != nullptr && !pindx->IsAssumdValid()) {
             Skip val
             *_VALID_
             valid.
            i (pindxFirstNotTransactionsValid == nullptr &&
                    (pindx->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_TRANSACTIONS) {
                pindxFirstNotTransactionsValid = pindx;
            }
            i (pindxFirstNotChainValid == nullptr &&
                    (pindx->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_CHAIN) {
                pindxFirstNotChainValid = pindx;
            }
            i (pindxFirstNotScriptsValid == nullptr &&
                    (pindx->nStatus & BLOCK_VALID_MASK) < BLOCK_VALID_SCRIPTS) {
                pindxFirstNotScriptsValid = pindx;
            }
        }