<!-- 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.
throw JSONRPCError(RPC_CLIENT_P2P_DISABLED, "Error: Peer-to-peer functionality missing or disabled");
    }
    if (!request.params[0].isNull() && !request.params[0].get_str().empty()) {
        throw JSONRPCError(RPC_INVALID_PARAMETER, "Dummy value must be set to \"\"");
    }
    UniValue sendTo = request.params[1].get_obj();
    int nMinDepth = 1;
    if (!request.params[2].isNull())
        nMinDepth = request.params[2].get_int();
    mapValue_t mapValue;
    if (!request.params[3].isNull() && !request.params[3].get_str().empty())
        mapValue["comment"] = request.params[3].get_str();
    UniValue subtractFeeFromAmount(UniValue::VARR);
    if (!request.params[4].isNull())
        subtractFeeFromAmount = request.params[4].get_array();
    CCoinControl coin_control;
    if (!request.params[5].isNull()) {
        coin_control.m_signal_bip125_rbf = request.params[5].get_bool();
    }
    if (!request.params[6].isNull()) {
        coin_control.m_confirm_target = ParseConfirmTarget(request.params[6]);
    }
    if (!request.params[7].isNull()) {
        if (!FeeModeFromString(request.params[7].get_str(), coin_control.m_fee_mode)) {
            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
        }
    }
    std::set<CTxDestination> destinations;
    std::vector<CRecipient> vecSend;
    CAmount totalAmount = 0;