#vulnerable code 
                                private static double evalPredict(RegressionTree tree, double[] x) throws HiveException,
            IOException {
        String opScript = tree.predictOpCodegen(StackMachine.SEP);
        debugPrint(opScript);
        DoubleWritable result = (DoubleWritable) TreePredictByStackMachineUDF.evaluate(opScript, x, false);
        return result.get();
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private static double evalPredict(RegressionTree tree, double[] x) throws HiveException,
            IOException {
        TreePredictByStackMachineUDF udf = new TreePredictByStackMachineUDF();
        String opScript = tree.predictOpCodegen(StackMachine.SEP);
        debugPrint(opScript);
        DoubleWritable result = (DoubleWritable) udf.evaluate(opScript, x, false);
        udf.close();
        return result.get();
    }