<!-- 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.
"]\n"
            "\nExamples:\n"
            + HelpExampleCli("listaddressgroupings", "")
            + HelpExampleRpc("listaddressgroupings", "")
        );
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK2(cs_main, pwallet->cs_wallet);
    UniValue jsonGroupings(UniValue::VARR);
    std::map<CTxDestination, CAmount> balances = pwallet->GetAddressBalances();
    for (const std::set<CTxDestination>& grouping : pwallet->GetAddressGroupings()) {
        UniValue jsonGrouping(UniValue::VARR);
        for (const CTxDestination& address : grouping)
        {
            UniValue addressInfo(UniValue::VARR);
            addressInfo.push_back(EncodeDestination(address));
            addressInfo.push_back(ValueFromAmount(balances[address]));
            {
                if (pwallet->mapAddressBook.find(address) != pwallet->mapAddressBook.end()) {
                    addressInfo.push_back(pwallet->mapAddressBook.find(address)->second.name);
                }
            }
            jsonGrouping.push_back(addressInfo);
        }
        jsonGroupings.push_back(jsonGrouping);
    }
    return jsonGroupings;
}
static UniValue signmessage(const JSONRPCRequest& request)