fixed bug in wrap-around

src/Kaleidoscope-LEDControl.cpp

@@ -37,13 +37,14 @@ void LEDControl::next_mode(void) {
 void LEDControl::prev_mode(void) {
   if (mode == 0) {
     // wrap around
-    mode = LED_MAX_MODES;
+    mode = LED_MAX_MODES - 1;
     // then  count down until reaching a valid mode
     while (mode > 0 && !modes[mode]) mode--;
   } else {
     mode--;
   }
-  set_mode(mode);
+
+  return set_mode(mode);
 }
 
 void