message: Improve error logging in CreateAnonCoinStake
diff: @@ -6711,10 +6711,10 @@ bool CWallet::CreateAnonCoinStake(unsigned int nBits, int64_t nSearchInterval, i
  {
  int oaoRingIndex;
  if (!AddAnonInput(txNew.vin[iVin], *pickedCoin, RING_SIG_2, nRingSize, oaoRingIndex, true, false, sError))
  - return false;
  + return error(("CreateAnonCoinStake : " + sError).c_str());
  if (!GenerateRingSignature(txNew.vin[iVin], RING_SIG_2, nRingSize, oaoRingIndex, preimage, sError))
  - return false;
  + return error(("CreateAnonCoinStake : " + sError).c_str());
  iVin++;
  }
  