Joystick size cannot be reduced via the "button size" slider button.

Steps to Reproduce:

1. Enable the new touch controls in Settings > Touch
2. Notice the size of the joystick
3. Set the "Button Size" slider to 0 in Settings > Touch
4. Notice the size of the joystick

Observed Results:
The joystick size is the same as before.

Expected Results:
The "Button Size" slider should affect the size of the joystick.