"Cannot read the array length because "" is null"

Question

Teacher provided me with a code to join all data from a file into a .csv file. it should work, but keeps throwing me a

"Cannot read the array length because "" is null" exception. here:

for (File ap : directorio.listFiles())

i know this has been answered in other threads, but cant find the error here, and teacher isnt available anymore. The ide is also giving me a small warning about the first if, telling me it is not necessary, but i dont think it is related.

if (directorio == null)

The full code is shown here:

public class JuntaDatosAP {

    
    static String dirBase = "G:\\DATA\\data.2018000\\DATA.2018000";
    static String archivoSalida = "G:\\DATA\\data2018000.csv";

    static int numRegistros = 0;

    public static void main(String[] args) {
        File directorio = new File(dirBase);
        if (directorio == null) {
            System.out.println("Directorio base no existe.");
            System.out.println(dirBase);
            System.exit(1);
        }

        try(FileOutputStream fos = new FileOutputStream(archivoSalida, true)) {
            PrintWriter pw = new PrintWriter(fos);



//Exception throwed down here

            for (File ap : directorio.listFiles()) {
                if (ap.isDirectory() && ap.getName().split("_").length != 6) {
                    System.out.println("Directorio no es un AP");
                    System.out.println(ap.getName());
                } else {
                    System.out.println("Procesando " + ap.getName());
                    procesaAP(ap, pw);
                }
            }
        } catch (FileNotFoundException ex) {
            Logger.getLogger(JuntaDatosAP.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException ex) {
            Logger.getLogger(JuntaDatosAP.class.getName()).log(Level.SEVERE, null, ex);
        }
    }

    private static void procesaAP(File ap, PrintWriter pw) {
        String linea;

        File dirs = new File(ap.getAbsolutePath());
        File[] dirsAux = dirs.listFiles();
        for (File dirs2 : dirsAux) {
            System.out.println(dirs2.getName());
            String fecha[] = dirs2.getName().split("_");
            fecha = fecha[6].split("T");
            String dia = fecha[0];
            String hora = fecha[1];
            File archs = new File(dirs2.getAbsolutePath());
            File[] archsAux = archs.listFiles();
            for (File arch : archsAux) {
                BufferedReader br;
                try {
                    String datos[];
                    br = new BufferedReader(new FileReader(arch.getAbsolutePath()));
                    while ((linea = br.readLine()) != null) {
                        numRegistros++;
                        datos = linea.split(",");
                        // Simplemente escribo la nueva línea en el archivo, separada por comas
                        pw.println(ap.getName() + "," + linea);
                    }
                    br.close();
                } catch (FileNotFoundException ex) {
                    Logger.getLogger(JuntaDatosAP.class.getName()).log(Level.SEVERE, null, ex);
                } catch (IOException ex) {
                    Logger.getLogger(JuntaDatosAP.class.getName()).log(Level.SEVERE, null, ex);
                }
            }
        }
        System.out.println("Total registros: " + numRegistros);
        System.out.println("");
    }
}