Fix indexing of null values #275

	name: Black
	on: [push]
	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	fail-fast: false
	matrix:
	python-version: [3.8]
	black-version: ["21.11b1"]
	click-version: ["8.0.4"]

	steps:
	# git checkout
	- uses: actions/checkout@v2

	# python setup
	- name: Set up Python ${{ matrix.python-version }}
	uses: actions/setup-python@v1
	with:
	python-version: ${{ matrix.python-version }}

	# python cache
	- uses: actions/cache@v1
	with:
	path: ~/.cache/pip
	key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
	restore-keys: \|
	${{ runner.os }}-pip-

	# install black
	- name: install black
	run: pip install click==${{ matrix.click-version }} black==${{ matrix.black-version }}

	# run black
	- name: run black
	run: black src/ --check --diff

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