#vulnerable code 
                                public void saveAll() throws FileNotFoundException, UnsupportedEncodingException {
        for (CompilationUnit cu : compilationUnits) {
            Path filename = cu.getData(ORIGINAL_LOCATION);
            System.out.println("Saving " + filename);
            filename.getParent().toFile().mkdirs();
            String code = new PrettyPrinter().print(cu);
            try (PrintWriter out = new PrintWriter(filename.toFile(), UTF8.toString())) {
                out.println(code);
            }
        }
    } 
                            #location 5 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void saveAll() throws FileNotFoundException, UnsupportedEncodingException {
        saveAll(root);
    }