Erro ao invocar o metodo Bitmap.createScaledBitmap

Ao executar o app é me retornado o seguinte erro 'Attempt to invoke virtual method 'int android.graphics.Bitmap.getWidth()' on a null object reference'.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <ImageView
        android:id="@+id/list_item_foto"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@drawable/person"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:gravity="center_vertical">

        <TextView
            android:id="@+id/list_item_nome"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Nome"
            android:textSize="20sp"
            android:textStyle="bold"
            android:paddingLeft="10dp"/>

        <TextView
            android:id="@+id/list_item_telefone"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Telefone"
            android:textSize="18sp"
            android:paddingLeft="16dp"
            android:textStyle="bold"
            android:paddingTop="8dp"/>
    </LinearLayout>


</LinearLayout>

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Aluno aluno = alunos.get(position);
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = convertView;
        if(view == null){
             view = inflater.inflate(R.layout.list_item_alunos, parent, false);
        }

        TextView campoNome = (TextView) view.findViewById(R.id.list_item_nome);
        campoNome.setText(aluno.getNome());

        TextView campoTelefone = (TextView) view.findViewById(R.id.list_item_telefone);
        campoTelefone.setText(aluno.getTelefone());

        ImageView campoFoto = (ImageView) view.findViewById(R.id.list_item_foto);
        String caminhoFoto = aluno.getCaminhoFotoAluno();
        if(caminhoFoto != null){
            Bitmap bitmap = BitmapFactory.decodeFile(caminhoFoto);
            Bitmap bitmapReduzido = Bitmap.createScaledBitmap(bitmap, 100, 100,true);
            campoFoto.setImageBitmap(bitmapReduzido);
            campoFoto.setScaleType(ImageView.ScaleType.FIT_XY);
        }
        return view;
    }