message: Add lock for dgp gas retrieval
diff: @@ -195,6 +195,8 @@ QString ClientModel::getStatusBarWarnings() const
  void ClientModel::getGasInfo(uint64_t& blockGasLimit, uint64_t& minGasPrice, uint64_t& nGasPrice) const
  {
  + LOCK(cs_main);
  +
  QtumDGP qtumDGP(globalState.get(), fGettingValuesDGP);
  blockGasLimit = qtumDGP.getBlockGasLimit(chainActive.Height());
  minGasPrice = CAmount(qtumDGP.getMinGasPrice(chainActive.Height()));
  