I kind of suck at boolean algebra, but:
https://github.com/bitcoin/bitcoin/blob/37612099ec7314b15a07d8bac55161ed4e8e7491/src/rpc/rawtransaction.cpp#L1672


Unless I'm mistaken (which is highly likely) the whole thing can't work  (except the edge case where `permitsigdata=true` and you have no sig data) 
{
    
    CCoinsView viewDummy;
    CCoinsViewCache view(&viewDummy);
    {
        LOCK2(cs_main, mempool.cs);
        CCoinsViewCache &viewChain = *pcoinsTip;
        CCoinsViewMemPool viewMempool(&viewChain, mempool);
        view.SetBackend(viewMempool); 
        for (const CTxIn& txin : mtx.vin) {
            view.AccessCoin(txin.prevout); 
        }
        view.SetBackend(viewDummy); 
    }
    
    if (!prevTxsUnival.isNull()) {
        UniValue prevTxs = prevTxsUnival.get_array();
        for (unsigned int idx = 0; idx < prevTxs.size(); ++idx) {
            const UniValue& p = prevTxs[idx];
            if (!p.isObject()) {
                throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "expected object with {\"txid'\",\"vout\",\"scriptPubKey\"}");
            }
            UniValue prevOut = p.get_obj();
            RPCTypeCheckObj(prevOut,
                {
                    {"txid", UniValueType(UniValue::VSTR)},
                    {"vout", UniValueType(UniValue::VNUM)},
                    {"scriptPubKey", UniValueType(UniValue::VSTR)},