message: fix a small bug of starting ghttp with a database built unsuccessfully
diff: @@ -789,6 +789,13 @@ int initialize(int argc, char *argv[])
  cout << "Database " << database << ".db has not been built." << endl;
  return -1;
  }
  + if (!boost::filesystem::exists(database + ".db/success.txt"))
  + {
  + cout << "Database " << database << ".db has not been built successfully." << endl;
  + string cmd = "rm -r " + database + ".db";
  + system(cmd.c_str());
  + return -1;
  + }
  bool flag = current_database->load();
  if (!flag)
  