PreparedStatementWrapper - second close method executing:null

protected int executeImpl(Long treeNodeId, Long parentTreeNodeId, InetTariffRequest req, InetTariffContext context, TreeContext treeContext, InetTariffWorkerContext workerContext)
{

   byte contractBalanceMode = Contract.CREDIT_BALANCE_MODE;

   ServerContext serverContext = ServerContext.get();
   if( context != null ) {
      ContractService contractService = (ContractService)serverContext.getService(ContractService.class, 0);
      Contract contract = contractService.contractGet(req.cid);
      if( contract != null ) {
         contractBalanceMode = (byte)(contract).getBalanceMode();
      } else {
         logger.error("Contract is null");
      }
   }
   switch(contractBalanceMode)
   {
      case Contract.CREDIT_BALANCE_MODE:
         return 1;
      case Contract.DEBET_BALANCE_MODE:
      default:
         return 0;
   }
}