<!-- Describe the issue -->

When trying to sign a transaction in a encrypted wallet that is locked, version 0.16 would return the following error:

```"Please enter the wallet passphrase with walletpassphrase first."```

While doing exactly the same procedure against 0.17, the response is something like:

```json
"hex": "020000000183ac9cc1137c444f32356fb070ecba194c87a05e43674c06a55f5b1d0561eabc0000000000ffffffff0180626a94000000001600141875aa6ab19c2551c11759cf3e9f4dd7aa40bcf500000000",
       "complete": false,
       "errors": [
         {
           "txid": "bcea61051d5b5fa5064c67435ea0874c19baec70b06f35324f447c13c19cac83",
           "vout": 0,
           "witness": [
           ],
           "scriptSig": "",
           "sequence": 4294967295,
           "error": "Unable to sign input, invalid stack size (possibly missing key)"
         }
     ]

```

<!--- What behavior did you expect? -->

v0.17 should check if the wallet is locked before trying to sign the tx and return the same error as v0.16 for consistency reasons.
if (!IsValidDestination(dest)) {
        throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Invalid Bitcoin address");
    }
    std::string label = LabelFromValue(request.params[1]);
    if (IsMine(*pwallet, dest)) {
        pwallet->SetAddressBook(dest, label, "receive");
    } else {
        pwallet->SetAddressBook(dest, label, "send");
    }
    return NullUniValue;
}
static CTransactionRef SendMoney(CWallet * const pwallet, const CTxDestination &address, CAmount nValue, bool fSubtractFeeFromAmount, const CCoinControl& coin_control, mapValue_t mapValue)
{
    CAmount curBalance = pwallet->GetBalance();
    
    if (nValue <= 0)
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid amount");
    if (nValue > curBalance)
        throw JSONRPCError(RPC_WALLET_INSUFFICIENT_FUNDS, "Insufficient funds");
    if (pwallet->GetBroadcastTransactions() && !g_connman) {
        throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
    }
    
    CScript scriptPubKey = GetScriptForDestination(address);
    
    CReserveKey reservekey(pwallet);
    CAmount nFeeRequired;
    std::string strError;
    std::vector<CRecipient> vecSend;
    int nChangePosRet = -1;