<!-- 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.
}
    }
    
    if (fPruneMode) {
        LOCK(cs_main);
        CBlockIndex *block = pindexStop ? pindexStop : pChainTip;
        while (block && block->nHeight >= pindexStart->nHeight) {
            if (!(block->nStatus & BLOCK_HAVE_DATA)) {
                throw JSONRPCError(RPC_MISC_ERROR, "Can't rescan beyond pruned data. Use RPC call getblockchaininfo to determine your pruned height.");
            }
            block = block->pprev;
        }
    }
    CBlockIndex *stopBlock = pwallet->ScanForWalletTransactions(pindexStart, pindexStop, reserver, true);
    if (!stopBlock) {
        if (pwallet->IsAbortingRescan()) {
            throw JSONRPCError(RPC_MISC_ERROR, "Rescan aborted.");
        }
        
        stopBlock = pindexStop ? pindexStop : pChainTip;
    }
    else {
        throw JSONRPCError(RPC_MISC_ERROR, "Rescan failed. Potentially corrupted data files.");
    }
    UniValue response(UniValue::VOBJ);
    response.pushKV("start_height", pindexStart->nHeight);
    response.pushKV("stop_height", stopBlock->nHeight);
    return response;
}
class DescribeWalletAddressVisitor : public boost::static_visitor<UniValue>