Possible to end up with a NoneType for keyboard_layout

[caternuson]

Currently, the keyboard_layout member is only init'd if keyboard is None:

Adafruit_CircuitPython_MacroPad/adafruit_macropad.py

Lines 406 to 410 in 21def3e

	if self._keyboard is None:
	self._keyboard = Keyboard(usb_hid.devices)
	# This will need to be updated if we add more layouts. Currently there is only US.
	self._keyboard_layout = KeyboardLayoutUS(self._keyboard)
	return self._keyboard_layout

This can result in getting a None return if other calls have been done which initialize keyboard.

Example:

Adafruit CircuitPython 7.0.0-alpha.5 on 2021-07-21; Adafruit Macropad RP2040 with rp2040
>>> from adafruit_macropad import MacroPad
>>> macropad = MacroPad()
>>> macropad.keyboard.send(0x04)
>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined
>>> macropad.keyboard_layout.write("hello world")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'NoneType' object has no attribute 'write'
>>>