Steps to reproduce:

* Build with `integer` sanitizer
* Start: `UBSAN_OPTIONS="suppressions=$(pwd)/test/sanitizer_suppressions/ubsan:print_stacktrace=1:halt_on_error=1:report_error_type=1" ./src/qt/bitcoin-qt -chain=main`
* Enter `getdescriptorinfo "sh(multi(1,xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/5/5/5/2/8/5/8/8/8/2/2/5/8/5/2/5/85/58/5/2/5/5/5/5/2/58/2/5/8/0000/00/8/5/2/001/1/246/8/501/46/8/5/8/5/000/8/52/5/8/5/2/8/2/5/8/5/246/8/5/2/8/2/5/8/5/2/5/8/8/2/5/5/5/58/88/2/6/8/5/2/8/2/5/8/2/588/5/2/5/8/5/2/8/5/1/5/4/5/5/5/2/6/8/5/2/8/2/5/8/5/2/5/58/58/2/5/8/58/588/2/52/5/5/5/58/8/2/6/8/5/2/8/2/5/8/2/588/5/2/5/8/5/2/8/5/15/58/58/2/6/8/5/2/8/2/5/8/5/2/5/8/58/2/5/58/58/588/2/5/2/8/5/8/5/4/5/58/588/2/6/8/5/2/8/2/5/8/2/8/5/2/8/2/5/8/5/2/5/58/58/2/5/5/5/58/588/2/6/8/5/2/8/2/5/8/2/8/588/2/6/8/5/2/8/2/5/5/8/5/2/0/8/5/2/00/4/5/5/588/2/6/8/5/2/8/25/5/8/2/5/58/58/8/4/1,[00000000]xprv9uPDJpEQgRQfDcW7BkF7eTya6RPxXeJCqCJGHuCJ4GiRVLzkTXBAJMu2qaMWPrS7AANYqdq6vcBcBUdJCVVFceUvJFjaPdGZ2y9WACViL4L/58)0)"` into the console
error = strprintf("Multi: expected ',', got '%c'", expr[0]);
                return nullptr;
            }
            auto arg = Expr(expr);
            auto pk = ParsePubkey(key_exp_index, arg, ctx, out, error);
            if (!pk) {
                error = strprintf("Multi: %s", error);
                return nullptr;
            }
            script_size += pk->GetSize() + 1;
            providers.emplace_back(std::move(pk));
            key_exp_index++;
        }
        if ((multi || sortedmulti) && (providers.empty() || providers.size() > MAX_PUBKEYS_PER_MULTISIG)) {
            error = strprintf("Cannot have %u keys in multisig; must have between 1 and %d keys, inclusive", providers.size(), MAX_PUBKEYS_PER_MULTISIG);
            return nullptr;
        } else if ((multi_a || sortedmulti_a) && (providers.empty() || providers.size() > MAX_PUBKEYS_PER_MULTI_A)) {
            error = strprintf("Cannot have %u keys in multi_a; must have between 1 and %d keys, inclusive", providers.size(), MAX_PUBKEYS_PER_MULTI_A);
            return nullptr;
        } else if (thres < 1) {
            error = strprintf("Multisig threshold cannot be %d, must be at least 1", thres);
            return nullptr;
        } else if (thres > providers.size()) {
            error = strprintf("Multisig threshold cannot be larger than the number of keys; threshold is %d but only %u keys specified", thres, providers.size());
            return nullptr;
        }
        if (ctx == ParseScriptContext::TOP) {
            if (providers.size() > 3) {
                error = strprintf("Cannot have %u pubkeys in bare multisig; only at most 3 pubkeys", providers.size());
                return nullptr;