#vulnerable code 
                                protected void writeToArchive(File[] sources, ArchiveOutputStream archive) throws IOException {
        for (File source : sources) {
            if (!source.exists()) {
                throw new FileNotFoundException(source.getPath());
            } else if (!source.canRead()) {
                throw new FileNotFoundException(source.getPath() + " (Permission denied)");
            }

            if (source.isFile()) {
                writeToArchive(source.getParentFile(), new File[]{ source }, archive);
            } else {
                writeToArchive(source, source.listFiles(), archive);
            }
        }
    } 
                            #location 12 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                protected void writeToArchive(File[] sources, ArchiveOutputStream archive) throws IOException {
        for (File source : sources) {
            if (!source.exists()) {
                throw new FileNotFoundException(source.getPath());
            } else if (!source.canRead()) {
                throw new FileNotFoundException(source.getPath() + " (Permission denied)");
            }

            writeToArchive(source.getParentFile(), new File[]{ source }, archive);
        }
    }