Change currentPreset to byte

JSON API still returns -1 for no preset

wled00/led.cpp

@@ -111,7 +111,7 @@ void colorUpdated(int callMode)
   {
     effectChanged = false;
     if (realtimeTimeout == UINT32_MAX) realtimeTimeout = 0;
-    currentPreset = -1; //something changed, so we are no longer in the preset
+    currentPreset = 0; //something changed, so we are no longer in the preset
         
     notify(callMode);