Modifying contents of a displayio.Group causes a hard crash

[kmatch98]

The following code causes a hard crash when the group element is changed:

import time
time.sleep(5) # allow time to Ctrl-C if you need to

import displayio

my_group=displayio.Group()
bitmap1=displayio.Bitmap(1,1,2)
palette=displayio.Palette(2)
tilegrid1=displayio.TileGrid(bitmap1, pixel_shader=palette)
tilegrid2=displayio.TileGrid(bitmap1, pixel_shader=palette)

print('appending')
my_group.append(tilegrid1)

print('len(my_group): {}'.format(len(my_group)))

print('mutating my_group[0]')
my_group[0]=tilegrid2

print('entering loop')
while True:
    pass

Here's what shows up on the display before the crash:

>>> 
soft reboot

Auto-reload is on. Simply save files over USB to run them or enter REPL to disable.

code.py output:
appending
len(my_group): 1
mutating my_group[0]

Hardware: PyPortal
Version:

Adafruit CircuitPython 6.2.0-beta.2-302-gcd48c5ee8 on 2021-03-03; Adafruit PyPortal with samd51j20

Possibly related to #4233