Null exception in pass bundles string between activities from service

public Integer thumbs = R.drawable.computer;
private Context con=null;
private LstClients clients = null;
private Server ser=null;

public DeviceAdaptor(Context c, Server ser){
	con = c;
	this.ser = ser;
	this.clients= this.ser.Clients();
}

public View getView(int arg0, View view, ViewGroup arg2) {
	// TODO Auto-generated method stub

	if(view==null){
		LayoutInflater inflator = ((Activity)con).getLayoutInflater();
		view = inflator.inflate(R.layout.activity_device_info, arg2,false);

	}
	
	TextView deviceName = (TextView)view.findViewById(R.id.lblDeviceName);
	tmp=arg0;
            deviceName.setText(clients.Name(arg0));
            ImageView img = (ImageView)view.findViewById(R.id.imgDevice);
            img.setImageResource(R.drawable.computer);
            img.setOnClickListener(new OnClickListener() {
		
		@Override
		public void onClick(View arg0) {
		
			ser.FindClients().interact.get(tmp).start();
			Intent in = new Intent((Activity)con  , FileManagerActivity.class);
			in.putExtra("Nmbr",tmp);
			con.startActivity(in);
			Log.e("DEVICEADAPTOR", "Moved");
			
		}
	});
    return view;
}

public boolean onCreateOptionsMenu(Menu menu) {

    getMenuInflater().inflate(R.menu.file_manager, menu);
    Log.e("FILEMANAGERACTIVITY", "starting");
    Bundle bn = null;
    a= getIntent().getIntExtra("Nmbr", 0);
    Log.e("FILEMANAGERACTIVITY", String.valueOf(a));
    Start();

    return true;
}