LEDOff: Always set everything to off

While it was a neat optimization to only turn LEDs off at init time, that is not
enough if there are other plugins in play, that work with the LEDs independently
of the active LED mode. Such a plugin is LED-ActiveModColor, which never turns
LEDs off, and relies on the LED mode to do that.

Since LEDOff did not turn things off on update(), when used together with
LED-ActiveModColor, the LEDs under the modifiers stayed active, even after the
modifiers went inactive.

With this simple change, LEDOff will now update, and the problem's gone.

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

src/LED-Off.cpp

@@ -1,3 +1,7 @@
 #include "LED-Off.h"
 
+void LEDOff_::update (void) {
+  LEDControl.set_all_leds_to ({0, 0, 0});
+}
+
 LEDOff_ LEDOff;

src/LED-Off.h

@@ -5,6 +5,8 @@
 class LEDOff_ : public LEDMode {
  public:
   LEDOff_ (void) { };
+
+  virtual void update (void) final;
 };
 
 extern LEDOff_ LEDOff;