This is really a non-issue.
It would have been nice if the resistor is on the transistor's base.
But even if it is not, you can still control the backlight via the pin (D10): first, clear D10. After that, if you wish to turn on the back light, turn D10 into an input - the pull-up resistor will now turn on the switch / led; if you wish to turn off the back light, turn D10 into an output - now, D10 will be cleared thus turning off the switch / led.
If you do that in a timer, you can do software PWM and control the backlight brightness continuously.