#vulnerable code 
                             public List<Transformer> getTransformers(){
		List<Object[]> steps = getSteps();
		boolean flexible = isFlexible();

		if(flexible && steps.size() > 0){
			Estimator estimator = getEstimator();

			if(estimator != null){
				steps = steps.subList(0, steps.size() - 1);
			}
		}

		return TransformerUtil.asTransformerList(TupleUtil.extractElementList(steps, 1));
	} 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             public List<Transformer> getTransformers(){
		List<Object[]> steps = getSteps();

		return TransformerUtil.asTransformerList(TupleUtil.extractElementList(steps, 1));
	}