message: estimatesmartfee to return minimum amount if not enough data available
diff: #include <net.h>
  #include <outputtype.h>
  #include <policy/fees.h>
  +#include <policy/policy.h> // DEFAULT_BLOCK_MIN_TX_FEE
  #include <pow.h>
  #include <pos.h>
  #include <primitives/transaction.h>
  @@ -1159,12 +1160,11 @@ static UniValue estimatesmartfee(const JSONRPCRequest& request)
  UniValue errors(UniValue::VARR);
  FeeCalculation feeCalc;
  CFeeRate feeRate = ::feeEstimator.estimateSmartFee(conf_target, &feeCalc, conservative);
  - if (feeRate != CFeeRate(0)) {
  - result.pushKV("feerate", ValueFromAmount(feeRate.GetFeePerK()));
  - } else {
  - errors.push_back("Insufficient data or no feerate found");
  - result.pushKV("errors", errors);
  + auto minFee = CFeeRate(DEFAULT_BLOCK_MIN_TX_FEE);
  + if (feeRate < minFee) {
  + feeRate = minFee;
  }
  + result.pushKV("feerate", ValueFromAmount(feeRate.GetFeePerK()));
  result.pushKV("blocks", feeCalc.returnedTarget);
  return result;
  }
  