NeoPixels don't set to off when component removed or strand length updated

[tyeth]

Changing the length of a neopixel component or removing it doesn't turn off the unused pixels.
We should probably send a fill of off, then if needed set the new pixel values.

Found testing Mini Sparkle Motion

[brentru]

Is this something that should be implemented on the firmware-side or the IO-side?

[tyeth]

In my head we're getting an update message (or maybe remove then add), but we only set a new value for colour when a new colour is sent. If the user changes number then we should copy the current brightness and colour after quickly setting all (max pixels supported) to off to cover any now unused pixels.
It was noticeable that going up and down in strand length didnt behave as expected, possibly until after a reboot, so maybe IO side, but seen when adding a second chain of 240 to an existing one of 256