output: #fixed code
                                  public void beginTask(@Param(ScoreLangConstants.TASK_INPUTS_KEY) List<Input> taskInputs,
                            @Param(ScoreLangConstants.LOOP_KEY) LoopStatement loop,
                            @Param(ScoreLangConstants.RUN_ENV) RunEnvironment runEnv,
                            @Param(EXECUTION_RUNTIME_SERVICES) ExecutionRuntimeServices executionRuntimeServices,
                            @Param(ScoreLangConstants.NODE_NAME_KEY) String nodeName,
                            @Param(ExecutionParametersConsts.RUNNING_EXECUTION_PLAN_ID) Long RUNNING_EXECUTION_PLAN_ID,
                            @Param(ScoreLangConstants.NEXT_STEP_ID_KEY) Long nextStepId,
                            @Param(ScoreLangConstants.REF_ID) String refId) {
          try {
              startStepExecutionPathCalc(runEnv);
              runEnv.removeCallArguments();
              runEnv.removeReturnValues();
  
              Context flowContext = runEnv.getStack().popContext();
  
              Map<String, Serializable> flowVariables = flowContext.getImmutableViewOfVariables();
  
              fireEvent(executionRuntimeServices, runEnv, ScoreLangConstants.EVENT_INPUT_START, "Task inputs start Binding",
                      Pair.of(LanguageEventData.BOUND_INPUTS,(Serializable)retrieveInputs(taskInputs)),
                      Pair.of( LanguageEventData.levelName.TASK_NAME.name(), nodeName));
  
              //loops
              if (loopStatementExist(loop)) {
                  LoopCondition loopCondition = loopsBinding.getOrCreateLoopCondition(loop, flowContext, nodeName);
                  if (!loopCondition.hasMore()) {
                      runEnv.putNextStepPosition(nextStepId);
                      runEnv.getStack().pushContext(flowContext);
                      return;
                  }
  
                  if (loopCondition instanceof ForLoopCondition) {
                      ForLoopCondition forLoopCondition = (ForLoopCondition) loopCondition;
  
                      if (loop instanceof ListForLoopStatement) {
                          // normal iteration
                          String varName = ((ListForLoopStatement) loop).getVarName();
                          loopsBinding.incrementListForLoop(varName, flowContext, forLoopCondition);
                      } else {
                          // map iteration
                          MapForLoopStatement mapForLoopStatement = (MapForLoopStatement) loop;
                          String keyName = mapForLoopStatement.getKeyName();
                          String valueName = mapForLoopStatement.getValueName();
                          loopsBinding.incrementMapForLoop(keyName, valueName, flowContext, forLoopCondition);
                      }
                  }
              }
  
  //            Map<String, Serializable> flowVariables = flowContext.getImmutableViewOfVariables();
              Map<String, Serializable> operationArguments = inputsBinding.bindInputs(taskInputs, flowVariables, runEnv.getSystemProperties());
  
              //todo: hook
  
              sendBindingInputsEvent(taskInputs, operationArguments, runEnv, executionRuntimeServices, "Task inputs resolved",
                      nodeName, LanguageEventData.levelName.TASK_NAME);
  
              updateCallArgumentsAndPushContextToStack(runEnv, flowContext, operationArguments);
  
              // request the score engine to switch to the execution plan of the given ref
              requestSwitchToRefExecutableExecutionPlan(runEnv, executionRuntimeServices, RUNNING_EXECUTION_PLAN_ID, refId, nextStepId);
  
              // set the start step of the given ref as the next step to execute (in the new running execution plan that will be set)
              runEnv.putNextStepPosition(executionRuntimeServices.getSubFlowBeginStep(refId));
  //            runEnv.getExecutionPath().down();
          } catch (RuntimeException e) {
              logger.error("There was an error running the begin task execution step of: \'" + nodeName + "\'. Error is: " + e.getMessage());
              throw new RuntimeException("Error running: " + nodeName + ": " + e.getMessage(), e);
          }
      }
input: #vulnerable code 
                                  public void beginTask(@Param(ScoreLangConstants.TASK_INPUTS_KEY) List<Input> taskInputs,
                            @Param(ScoreLangConstants.LOOP_KEY) LoopStatement loop,
                            @Param(ScoreLangConstants.RUN_ENV) RunEnvironment runEnv,
                            @Param(EXECUTION_RUNTIME_SERVICES) ExecutionRuntimeServices executionRuntimeServices,
                            @Param(ScoreLangConstants.NODE_NAME_KEY) String nodeName,
                            @Param(ExecutionParametersConsts.RUNNING_EXECUTION_PLAN_ID) Long RUNNING_EXECUTION_PLAN_ID,
                            @Param(ScoreLangConstants.NEXT_STEP_ID_KEY) Long nextStepId,
                            @Param(ScoreLangConstants.REF_ID) String refId) {
          try {
              runEnv.getExecutionPath().forward();
              runEnv.removeCallArguments();
              runEnv.removeReturnValues();
  
              Context flowContext = runEnv.getStack().popContext();
  
              //loops
              if (loopStatementExist(loop)) {
                  LoopCondition loopCondition = loopsBinding.getOrCreateLoopCondition(loop, flowContext, nodeName);
                  if (!loopCondition.hasMore()) {
                      runEnv.putNextStepPosition(nextStepId);
                      runEnv.getStack().pushContext(flowContext);
                      return;
                  }
  
                  if (loopCondition instanceof ForLoopCondition) {
                      ForLoopCondition forLoopCondition = (ForLoopCondition) loopCondition;
  
                      if (loop instanceof ListForLoopStatement) {
                          // normal iteration
                          String varName = ((ListForLoopStatement) loop).getVarName();
                          loopsBinding.incrementListForLoop(varName, flowContext, forLoopCondition);
                      } else {
                          // map iteration
                          MapForLoopStatement mapForLoopStatement = (MapForLoopStatement) loop;
                          String keyName = mapForLoopStatement.getKeyName();
                          String valueName = mapForLoopStatement.getValueName();
                          loopsBinding.incrementMapForLoop(keyName, valueName, flowContext, forLoopCondition);
                      }
                  }
              }
  
              Map<String, Serializable> flowVariables = flowContext.getImmutableViewOfVariables();
              Map<String, Serializable> operationArguments = inputsBinding.bindInputs(taskInputs, flowVariables, runEnv.getSystemProperties());
  
              //todo: hook
  
              sendBindingInputsEvent(taskInputs, operationArguments, runEnv, executionRuntimeServices, "Task inputs resolved",
                      nodeName, LanguageEventData.levelName.TASK_NAME);
  
              updateCallArgumentsAndPushContextToStack(runEnv, flowContext, operationArguments);
  
              // request the score engine to switch to the execution plan of the given ref
              requestSwitchToRefExecutableExecutionPlan(runEnv, executionRuntimeServices, RUNNING_EXECUTION_PLAN_ID, refId, nextStepId);
  
              // set the start step of the given ref as the next step to execute (in the new running execution plan that will be set)
              runEnv.putNextStepPosition(executionRuntimeServices.getSubFlowBeginStep(refId));
              runEnv.getExecutionPath().down();
          } catch (RuntimeException e) {
              logger.error("There was an error running the begin task execution step of: \'" + nodeName + "\'. Error is: " + e.getMessage());
              throw new RuntimeException("Error running: " + nodeName + ": " + e.getMessage(), e);
          }
      } 
                              #location 18 
                              #vulnerability type NULL_DEREFERENCE