#vulnerable code 
                             static
	public MiningModel encodeBooster(HasBooster hasBooster, Schema schema){
		Booster booster = hasBooster.getBooster();

		Learner learner = booster.getLearner();

		Schema xgbSchema = XGBoostUtil.toXGBoostSchema(schema);

		MiningModel miningModel = learner.encodeMiningModel(xgbSchema);

		return miningModel;
	} 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             static
	public MiningModel encodeBooster(HasBooster hasBooster, Schema schema){
		Booster booster = hasBooster.getBooster();

		Learner learner = booster.getLearner();

		Schema xgbSchema = XGBoostUtil.toXGBoostSchema(schema);

		// XXX
		List<Feature> features = xgbSchema.getFeatures();
		for(Feature feature : features){

			if(feature instanceof ContinuousFeature){
				SkLearnEncoder encoder = (SkLearnEncoder)feature.getEncoder();

				TypeDefinitionField field = encoder.getField(feature.getName());

				if(!(OpType.CONTINUOUS).equals(field.getOpType())){
					field.setOpType(OpType.CONTINUOUS);
				}
			}
		}

		MiningModel miningModel = learner.encodeMiningModel(xgbSchema);

		return miningModel;
	}