Error java.lang.NullPointerException

an app launches the error java.lang.NullPointerException but I do not know what part of the code is wrong, I would appreciate it if you could help me, this is the code

private class ImagePagerAdapter extends PagerAdapter {

    private LayoutInflater inflater;

    public ImagePagerAdapter() {

        inflater = getLayoutInflater();
    }

    @Override
    public int getCount() {
        return mAllImages.length;

    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view.equals(object);
    }

    @Override
    public Object instantiateItem(ViewGroup container, int position) {

        View imageLayout = inflater.inflate(R.layout.viewpager_item, container, false);
        assert imageLayout != null;
        ImageView imageView = (ImageView) imageLayout.findViewById(R.id.image);
        final ProgressBar spinner = (ProgressBar) imageLayout.findViewById(R.id.loading);

        if(mAllImages[position].endsWith(".gif")) {
           // spinner.setVisibility(View.GONE);
            Glide.with(ActivitySlideImage.this).load(Config.SERVER_URL + "/upload/" +
                    mAllImages[position])
                    .diskCacheStrategy(DiskCacheStrategy.SOURCE)
                    .listener(new RequestListener<String, GlideDrawable>() {
                        @Override
                        public boolean onException(Exception e, String model, Target<GlideDrawable> target, boolean isFirstResource) {
                            spinner.setVisibility(View.GONE);
                            e.printStackTrace();
                            return false;
                        }

                        @Override
                        public boolean onResourceReady(GlideDrawable resource, String model, Target<GlideDrawable> target, boolean isFromMemoryCache, boolean isFirstResource) {
                            spinner.setVisibility(View.GONE);
                            resource.start();
                            return false;
                        }
                    })
                    .into(imageView);

        }else {
            Picasso.with(getApplicationContext()).load(Config.SERVER_URL + "/upload/" +
                    mAllImages[position]).placeholder(R.drawable.ic_thumbnail).into(imageView, new Callback() {
                @Override
                public void onSuccess() {


                    spinner.setVisibility(View.GONE);
                }

                @Override
                public void onError() {
                    Toast.makeText(ActivitySlideImage.this, "Error al cargar imagen", Toast.LENGTH_SHORT).show();
                    spinner.setVisibility(View.GONE);
                }
            });
        }



        container.addView(imageLayout, 0);
        return imageLayout;

    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        ((ViewPager) container).removeView((View) object);
    }
}

The error is this:

java.lang.NullPointerException
at com.solodroid.materialwallpaper.activities.ActivitySlideImage$ImagePagerAdapter$1.onException(ActivitySlideImage.java:501)
at com.solodroid.materialwallpaper.activities.ActivitySlideImage$ImagePagerAdapter$1.onException(ActivitySlideImage.java:497)
at com.bumptech.glide.request.GenericRequest.onException(GenericRequest.java:547)
at com.bumptech.glide.load.engine.EngineJob.handleExceptionOnMainThread(EngineJob.java:183)
at com.bumptech.glide.load.engine.EngineJob.access$200(EngineJob.java:22)
at com.bumptech.glide.load.engine.EngineJob$MainThreadCallback.handleMessage(EngineJob.java:204)