#vulnerable code 
                                public void readDirectory() {
        logger.log(Level.INFO, "Opening folder {0}", logFolder.getPath());
        logFileDir.clear();
        platforms.clear();

        if (logFolder.isFolder()) {
            Enumeration<? extends FileObject> children = logFolder.getChildren(true);

            while (children.hasMoreElements()) {
                FileObject file = children.nextElement();

                if (file.getNameExt().endsWith(".log") || file.getNameExt().endsWith(".log.gz")) {
                    try {
                        LogFile logFile = LogFile.fromFile(FileUtil.toFile(file));

                        if (platformList.containsKey(logFile.getPlatform())) {
                            ArrayList<LogFile> platform = platformList.get(logFile.getPlatform());
                            platform.add(logFile);
                        } else {
                            ArrayList<LogFile> platform = new ArrayList<LogFile>();
                            platform.add(logFile);
                            platformList.put(logFile.getPlatform(), platform);
                            platforms.add(logFile.getPlatform());
                        }
                    } catch (Exception ex) {
                        logger.log(Level.WARNING, "Found malformed log file: {0}. Ignoring...", file.getName());
                    }
                }
            }
        }
    } 
                            #location 16 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                public void readDirectory() {
        logger.log(Level.INFO, "Opening folder {0}", logFolder.getPath());
        logFileDir.clear();
        platforms.clear();

        if (logFolder.isFolder()) {
            Enumeration<? extends FileObject> children = logFolder.getChildren(true);

            while (children.hasMoreElements()) {
                FileObject file = children.nextElement();

                if (file.getNameExt().endsWith(".log") || file.getNameExt().endsWith(".log.gz")) {
                    try {
                        LogFile logFile = new LogFile(FileUtil.toFile(file));

                        if (platformList.containsKey(logFile.getPlatform())) {
                            ArrayList<LogFile> platform = platformList.get(logFile.getPlatform());
                            platform.add(logFile);
                        } else {
                            ArrayList<LogFile> platform = new ArrayList<LogFile>();
                            platform.add(logFile);
                            platformList.put(logFile.getPlatform(), platform);
                            platforms.add(logFile.getPlatform());
                        }
                    } catch (Exception ex) {
                        logger.log(Level.WARNING, "Found malformed log file: {0}. Ignoring...", file.getName());
                    }
                }
            }
        }
    }