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
if (!setConflictsParents.count(tx.vin[j].prevout.hash))
            {
                
                
                
                if (m_pool.exists(tx.vin[j].prevout.hash)) {
                    return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "replacement-adds-unconfirmed",
                            strprintf("replacement %s adds unconfirmed input, idx %d",
                                hash.ToString(), j));
                }
            }
        }
        
        
        
        if (nModifiedFees < nConflictingFees)
        {
            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
                    strprintf("rejecting replacement %s, less fees than conflicting txs; %s < %s",
                        hash.ToString(), FormatMoney(nModifiedFees), FormatMoney(nConflictingFees)));
        }
        
        
        CAmount nDeltaFees = nModifiedFees - nConflictingFees;
        if (nDeltaFees < ::incrementalRelayFee.GetFee(nSize))
        {
            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee",
                    strprintf("rejecting replacement %s, not enough additional fees to relay; %s < %s",