Delete Item from Cardview and sqlite database

I am trying to delete item from card view and database. This i have written for delete query in database helper class.

public List<DatabaseModel> deleteARow(String email){
    SQLiteDatabase db= this.getWritableDatabase();
    db.delete(STUDENT_TABLE, "email" + " = ?", new String[] { email });
    db.close();

}

On recyclerview view i have created on button called remove and on click of remove i want to call the above deleteARow(email) method. I am getting nullpointer exception when I click on button to remove item

 @Override
public void onBindViewHolder(RecyclerAdapter.ViewHolder holder, final int position) {

    holder.name.setText(dbList.get(position).getName());
    holder.email.setText(dbList.get(position).getEmail());


    holder.btnremove.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            String e=  dbList.get(position).getEmail().toString();
            dbList=  helpher.deleteARow(e);
            Intent intent = new Intent(v.getContext(), SecondActivity.class);

            v.getContext().startActivity(intent);

            Toast.makeText(RecyclerAdapter.context, "you have clicked Remove button ", Toast.LENGTH_LONG).show();
        }
    });

}