output: #fixed code
                               @Override
  	public List<Feature> encodeFeatures(List<String> ids, List<Feature> features, SkLearnEncoder encoder){
  		List<?> data = getData();
  
  		ClassDictUtil.checkSize(1, ids, features);
  
  		final
  		InvalidValueTreatmentMethod invalidValueTreatment = DomainUtil.parseInvalidValueTreatment(getInvalidValueTreatment());
  
  		WildcardFeature wildcardFeature = (WildcardFeature)features.get(0);
  
  		Function<Object, String> function = new Function<Object, String>(){
  
  			@Override
  			public String apply(Object object){
  				return ValueUtil.formatValue(object);
  			}
  		};
  
  		List<String> categories = Lists.transform(data, function);
  
  		FieldDecorator decorator = new ValidValueDecorator(){
  
  			{
  				setInvalidValueTreatment(invalidValueTreatment);
  			}
  		};
  
  		CategoricalFeature categoricalFeature = wildcardFeature.toCategoricalFeature(categories);
  
  		encoder.addDecorator(categoricalFeature.getName(), decorator);
  
  		return Collections.<Feature>singletonList(categoricalFeature);
  	}
input: #vulnerable code 
                               @Override
  	public List<Feature> encodeFeatures(List<String> ids, List<Feature> features, SkLearnEncoder encoder){
  		List<?> data = getData();
  
  		if(ids.size() != 1 || features.size() != 1){
  			throw new IllegalArgumentException();
  		}
  
  		final
  		InvalidValueTreatmentMethod invalidValueTreatment = DomainUtil.parseInvalidValueTreatment(getInvalidValueTreatment());
  
  		WildcardFeature wildcardFeature = (WildcardFeature)features.get(0);
  
  		Function<Object, String> function = new Function<Object, String>(){
  
  			@Override
  			public String apply(Object object){
  				return ValueUtil.formatValue(object);
  			}
  		};
  
  		List<String> categories = Lists.transform(data, function);
  
  		FieldDecorator decorator = new ValidValueDecorator(){
  
  			{
  				setInvalidValueTreatment(invalidValueTreatment);
  			}
  		};
  
  		CategoricalFeature categoricalFeature = wildcardFeature.toCategoricalFeature(categories);
  
  		encoder.addDecorator(categoricalFeature.getName(), decorator);
  
  		return Collections.<Feature>singletonList(categoricalFeature);
  	} 
                              #location 10 
                              #vulnerability type NULL_DEREFERENCE