<!-- 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.
}
    
    UniValue ret(UniValue::VARR);
    std::map<std::string, tallyitem> label_tally;
    
    
    auto start = pwallet->mapAddressBook.begin();
    auto end = pwallet->mapAddressBook.end();
    
    if (has_filtered_address) {
        start = pwallet->mapAddressBook.find(filtered_address);
        if (start != end) {
            end = std::next(start);
        }
    }
    for (auto item_it = start; item_it != end; ++item_it)
    {
        const CTxDestination& address = item_it->first;
        const std::string& label = item_it->second.name;
        auto it = mapTally.find(address);
        if (it == mapTally.end() && !fIncludeEmpty)
            continue;
        CAmount nAmount = 0;
        int nConf = std::numeric_limits<int>::max();
        bool fIsWatchonly = false;
        if (it != mapTally.end())
        {
            nAmount = (*it).second.nAmount;
            nConf = (*it).second.nConf;
            fIsWatchonly = (*it).second.fIsWatchonly;