https://github.com/bitcoin/bitcoin/blob/9ad6f14175c19b5d47267c3dd5840c14bad43c83/src/validation.cpp#L3711

If i'm following right the flow of the code, when we hit this lane `pindex` should be always equal to nullptr thus this check may be omitted
nullptr , true )) {
            
            
            mempool.removeRecursive(**it, MemPoolRemovalReason::REORG);
        } else if (mempool.exists((*it)->GetHash())) {
            vHashUpdate.push_back((*it)->GetHash());
        }
        ++it;
    }
    disconnectpool.queuedTx.clear();
    
    
    
    
    
    mempool.UpdateTransactionsFromBlock(vHashUpdate);
    
    mempool.removeForReorg(&::ChainstateActive().CoinsTip(), ::ChainActive().Tip()->nHeight + 1, STANDARD_LOCKTIME_VERIFY_FLAGS);
    
    LimitMempoolSize(mempool, gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000, std::chrono::hours{gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY)});
}
/**
* Checks to avoid mempool polluting consensus critical paths since cached
* signature and script validity results will be reused if we validate this
* transaction again during block validation.
* */
static bool CheckInputsFromMempoolAndCache(const CTransaction& tx, TxValidationState& state,
                const CCoinsViewCache& view, const CTxMemPool& pool,
                unsigned int flags, PrecomputedTransactionData& txdata)
                EXCLUSIVE_LOCKS_REQUIRED(cs_main, pool.cs)