<!-- Describe the issue -->
`getrawtransaction` fails
<!--- What behavior did you expect? -->
Return decoded raw tx
<!--- What was the actual behavior (provide screenshots if the issue is GUI-related)? -->
* `bitcoin-qt -prune=8192  -server -rpcuser=rpc -rpcpassword=rpc -onlynet=ipv4 -rpcbind=127.0.0.1:18332 -testnet`
  * BTC 0.18.0
  * `getrawtransaction b423b2b22d6d74376de2887c07f7c84ae890a93d541fcc6dbf3686f2923b2753 1`
![image](https://user-images.githubusercontent.com/3670331/58841021-658d7180-8668-11e9-9f9f-ed1f794070ea.png)
  * BTC 0.17.1
  * `getrawtransaction b423b2b22d6d74376de2887c07f7c84ae890a93d541fcc6dbf3686f2923b2753 1`
![image](https://user-images.githubusercontent.com/3670331/58841089-9ff70e80-8668-11e9-8a68-5022631b43d7.png)

<!--- How reliably can you reproduce the issue, what are the steps to do so? -->
Request `getrawtransaction`.
<!-- What version of Bitcoin Core are you using, where did you get it (website, self-compiled, etc)? -->
Official from site.
<!-- What type of machine are you observing the error on (OS/CPU and disk type)? -->
`Linux pentagon 4.9.0-9-amd64 #1 SMP Debian 4.9.168-1+deb9u2 (2019-05-13) x86_64 GNU/Linux`, u5200, 2x8Gb, SSD
<!-- For the GUI-related issue on Linux provide names and versions of a distro, a desktop environment and a graphical shell (if relevant). -->
QT
<!-- Any extra information that might be useful in the debugging process. -->
<!--- This is normally the contents of a `debug.log` or `config.log` file. Raw text or a link to a pastebin type site are preferred. -->

CCoinsViewMemPool viewMempool(&viewChain, mempool);
        view.SetBackend(viewMempool); 
        for (const CTxIn& txin : mergedTx.vin) {
            view.AccessCoin(txin.prevout); 
        }
        view.SetBackend(viewDummy); 
    }
    
    
    const CTransaction txConst(mergedTx);
    
    for (unsigned int i = 0; i < mergedTx.vin.size(); i++) {
        CTxIn& txin = mergedTx.vin[i];
        const Coin& coin = view.AccessCoin(txin.prevout);
        if (coin.IsSpent()) {
            throw JSONRPCError(RPC_VERIFY_ERROR, "Input not found or already spent");
        }
        SignatureData sigdata;
        
        for (const CMutableTransaction& txv : txVariants) {
            if (txv.vin.size() > i) {
                sigdata.MergeSignatureData(DataFromTransaction(txv, i, coin.out));
            }
        }
        ProduceSignature(DUMMY_SIGNING_PROVIDER, MutableTransactionSignatureCreator(&mergedTx, i, coin.out.nValue, 1), coin.out.scriptPubKey, sigdata);
        UpdateInput(txin, sigdata);
    }
    return EncodeHexTx(CTransaction(mergedTx));
}
static UniValue signrawtransactionwithkey(const JSONRPCRequest& request)