Transparency setting for shape fill color cannot be dynamically changed after initialization

[DavePutz]

This is a dup of issue #2076 in core (adafruit/circuitpython#2076) but the issue looks to be in the fill() routines for the various objects (rect, roundrect, and triangle).
An example program showing the issue:

import board
import displayio
import time
from adafruit_display_shapes.rect import Rect
from adafruit_display_shapes.circle import Circle
from adafruit_display_shapes.roundrect import RoundRect
from adafruit_display_shapes.triangle import Triangle

# Make the display context
splash = displayio.Group(max_size=10)
board.DISPLAY.show(splash)

# Make a background color fill
color_bitmap = displayio.Bitmap(320, 240, 1)
color_palette = displayio.Palette(1)
color_palette[0] = 0x333333
bg_sprite = displayio.TileGrid(color_bitmap, x=0, y=0,
pixel_shader=color_palette)
splash.append(bg_sprite)
##########################################################################

triangle = Triangle(170, 50, 120, 140, 210, 160, fill=0x00FF00, outline=0xFF00FF)
splash.append(triangle)

rect = Rect(80, 20, 41, 41, fill=0xFF0000)
splash.append(rect)

circle = Circle(100, 100, 20, fill=0x00FF00, outline=0xFF00FF)
splash.append(circle)

rect2 = Rect(50, 100, 61, 81, fill=None, outline=0x0, stroke=3)
splash.append(rect2)

roundrect = RoundRect(10, 10, 61, 81, 10, fill=0x00FFFF, outline=0xFF00FF, stroke=6)
splash.append(roundrect)

print("initial")
time.sleep(5)
while True:
print("first colors")
triangle.fill = 0xff0000
time.sleep(1)
rect.fill = 0x0000ff
time.sleep(1)
rect2.fill = 0x00FFff
time.sleep(1)
circle.fill = 0x789ABC
time.sleep(1)
roundrect.fill = 0xFFFFFF
time.sleep(5)
print("transparents")
triangle.fill = None
time.sleep(1)
rect.fill = None
time.sleep(1)
rect2.fill = 0xFF00FF
time.sleep(1)
roundrect.fill = None
time.sleep(1)
circle.fill = None
time.sleep(5)
print("second colors")
triangle.fill = 0x0000FF
time.sleep(1)
rect.fill = 0xFF0000
time.sleep(1)
rect2.fill = None
time.sleep(1)
circle.fill = 0x654321
time.sleep(1)
roundrect.fill = 0xFFFF00
time.sleep(5)

[makermelissa]

Fixed via #8