<!-- 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.
"\nExamples:\n"
            "\nBump the fee, get the new transaction\'s txid\n" +
            HelpExampleCli("bumpfee", "<txid>"));
    }
    RPCTypeCheck(request.params, {UniValue::VSTR, UniValue::VOBJ});
    uint256 hash;
    hash.SetHex(request.params[0].get_str());
    
    CAmount totalFee = 0;
    CCoinControl coin_control;
    coin_control.m_signal_bip125_rbf = true;
    if (!request.params[1].isNull()) {
        UniValue options = request.params[1];
        RPCTypeCheckObj(options,
            {
                {"confTarget", UniValueType(UniValue::VNUM)},
                {"totalFee", UniValueType(UniValue::VNUM)},
                {"replaceable", UniValueType(UniValue::VBOOL)},
                {"estimate_mode", UniValueType(UniValue::VSTR)},
            },
            true, true);
        if (options.exists("confTarget") && options.exists("totalFee")) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "confTarget and totalFee options should not both be set. Please provide either a confirmation target for fee estimation or an explicit total fee for the transaction.");
        } else if (options.exists("confTarget")) { 
            coin_control.m_confirm_target = ParseConfirmTarget(options["confTarget"]);
        } else if (options.exists("totalFee")) {
            totalFee = options["totalFee"].get_int64();
            if (totalFee <= 0) {
                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid totalFee %s (must be greater than 0)", FormatMoney(totalFee)));
            }