#vulnerable code 
                                public Long trigger(SlangTestCase testCase, CompilationArtifact compilationArtifact,
                        Map<String, ? extends Serializable> inputs,
                        Map<String, ? extends Serializable> systemProperties) {
        String testCaseName = testCase.getName();
        String result = testCase.getResult();

        //add start event
        Set<String> handlerTypes = new HashSet<>();
        handlerTypes.add(ScoreLangConstants.EVENT_EXECUTION_FINISHED);
        handlerTypes.add(ScoreLangConstants.SLANG_EXECUTION_EXCEPTION);
        handlerTypes.add(ScoreLangConstants.EVENT_OUTPUT_END);
        handlerTypes.add(EventConstants.SCORE_ERROR_EVENT);
        handlerTypes.add(EventConstants.SCORE_FAILURE_EVENT);
        handlerTypes.add(EventConstants.SCORE_FINISHED_EVENT);

        TriggerTestCaseEventListener testsEventListener = new TriggerTestCaseEventListener(testCaseName, result);
        slang.subscribeOnEvents(testsEventListener, handlerTypes);

        Long executionId = slang.run(compilationArtifact, inputs, systemProperties);

        while (!testsEventListener.isFlowFinished()) {
            try {
                Thread.sleep(200);
            } catch (InterruptedException ignore) {}
        }
        slang.unSubscribeOnEvents(testsEventListener);

        ReturnValues executionReturnValues = testsEventListener.getExecutionReturnValues();
        String executionResult = executionReturnValues.getResult();

        String errorMessageFlowExecution = testsEventListener.getErrorMessage();

        if(StringUtils.isBlank(errorMessageFlowExecution) && BooleanUtils.isTrue(testCase.getThrowsException())){
            throw new RuntimeException("Failed test: " + testCaseName + " - " + testCase.getDescription() + "\nFlow " + compilationArtifact.getExecutionPlan().getName() +" did not throw an exception as expected");
        }
        if(StringUtils.isNotBlank(errorMessageFlowExecution) && BooleanUtils.isFalse(testCase.getThrowsException())){
            // unexpected exception occurred during flow execution
            throw new RuntimeException("Error occured while running test: " + testCaseName + " - " + testCase.getDescription() + "\n" + errorMessageFlowExecution);
        }

        if (result != null && !executionResult.equals(result)){
            throw new RuntimeException("Failed test: " + testCaseName +" - " + testCase.getDescription() + "\nExpected result: " + result + "\nActual result: " + executionResult);
        }
        return executionId;
    } 
                            #location 41 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public Long trigger(SlangTestCase testCase, CompilationArtifact compilationArtifact,
                        Map<String, ? extends Serializable> inputs,
                        Map<String, ? extends Serializable> systemProperties) {
        String testCaseName = testCase.getName();
        String result = testCase.getResult();

        //add start event
        Set<String> handlerTypes = new HashSet<>();
        handlerTypes.add(ScoreLangConstants.EVENT_EXECUTION_FINISHED);
        handlerTypes.add(ScoreLangConstants.SLANG_EXECUTION_EXCEPTION);
        handlerTypes.add(ScoreLangConstants.EVENT_OUTPUT_END);
        handlerTypes.add(EventConstants.SCORE_ERROR_EVENT);
        handlerTypes.add(EventConstants.SCORE_FAILURE_EVENT);
        handlerTypes.add(EventConstants.SCORE_FINISHED_EVENT);

        TriggerTestCaseEventListener testsEventListener = new TriggerTestCaseEventListener(testCaseName, result);
        slang.subscribeOnEvents(testsEventListener, handlerTypes);

        Long executionId = slang.run(compilationArtifact, inputs, systemProperties);

        while (!testsEventListener.isFlowFinished()) {
            try {
                Thread.sleep(200);
            } catch (InterruptedException ignore) {}
        }
        slang.unSubscribeOnEvents(testsEventListener);

        ReturnValues executionReturnValues = testsEventListener.getExecutionReturnValues();
        String executionResult = executionReturnValues.getResult();

        String errorMessageFlowExecution = testsEventListener.getErrorMessage();

        if (BooleanUtils.isTrue(testCase.getThrowsException())) {
            if(StringUtils.isBlank(errorMessageFlowExecution)) {
                throw new RuntimeException("Failed test: " + testCaseName + " - " + testCase.getDescription() + "\nFlow " + compilationArtifact.getExecutionPlan().getName() +" did not throw an exception as expected");
            }
            return executionId;
        }

        if(StringUtils.isNotBlank(errorMessageFlowExecution)){
            // unexpected exception occurred during flow execution
            throw new RuntimeException("Error occured while running test: " + testCaseName + " - " + testCase.getDescription() + "\n" + errorMessageFlowExecution);
        }

        if (result != null && !result.equals(executionResult)){
            throw new RuntimeException("Failed test: " + testCaseName +" - " + testCase.getDescription() + "\nExpected result: " + result + "\nActual result: " + executionResult);
        }
        return executionId;
    }