<!-- 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.
CRecipient recipient = {scriptPubKey, nValue, fSubtractFeeFromAmount};
    vecSend.push_back(recipient);
    CTransactionRef tx;
    if (!pwallet->CreateTransaction(vecSend, tx, reservekey, nFeeRequired, nChangePosRet, strError, coin_control)) {
        if (!fSubtractFeeFromAmount && nValue + nFeeRequired > curBalance)
            strError = strprintf("Error: This transaction requires a transaction fee of at least %s", FormatMoney(nFeeRequired));
        throw JSONRPCError(RPC_WALLET_ERROR, strError);
    }
    CValidationState state;
    if (!pwallet->CommitTransaction(tx, std::move(mapValue), {} , reservekey, g_connman.get(), state)) {
        strError = strprintf("Error: The transaction was rejected! Reason given: %s", FormatStateMessage(state));
        throw JSONRPCError(RPC_WALLET_ERROR, strError);
    }
    return tx;
}
static UniValue sendtoaddress(const JSONRPCRequest& request)
{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() < 2 || request.params.size() > 8)
        throw std::runtime_error(
            "sendtoaddress \"address\" amount ( \"comment\" \"comment_to\" subtractfeefromamount replaceable conf_target \"estimate_mode\")\n"
            "\nSend an amount to a given address.\n"
            + HelpRequiringPassphrase(pwallet) +
            "\nArguments:\n"
            "1. \"address\"            (string, required) The bitcoin address to send to.\n"
            "2. \"amount\"             (numeric or string, required) The amount in " + CURRENCY_UNIT + " to send. eg 0.1\n"