fix rainbowchase on large strips (eg 512)

Author: rhooper

adafruit_led_animation/animation/rainbowchase.py

@@ -78,7 +78,7 @@ def __init__(
         super().__init__(pixel_object, speed, 0, size, spacing, reverse, name)
 
     def bar_color(self, n, pixel_no=0):
-        return self._colors[self._color_idx - n]
+        return self._colors[self._color_idx - (n % len(self._colors))]
 
     def on_cycle_complete(self):
         self._color_idx = (self._color_idx + self._direction) % len(self._colors)