fixed bug just introduced
fixed bug just introduced

 - only take off (shift) data if data was added

idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017,idcrook/rpi-iot-demo-2017