Use Date.no_date() instead of None for Task.date_due #413

	# Run unit tests script

	name: Unit Tests

	on:
	push:
	branches: [ master ]
	pull_request:
	branches: [ master ]
	jobs:
	build:
	runs-on: ubuntu-22.04
	steps:
	- uses: actions/checkout@v4
	- name: Set up Python 3.8
	uses: actions/setup-python@v5
	with:
	python-version: "3.8"
	- name: Install dependencies
	run: \|
	python -m pip install --upgrade pip
	sudo apt-get update
	sudo apt install -y meson gettext itstool libgirepository1.0-dev gir1.2-gtk-4.0 libgtksourceview-5-dev libportal-dev
	pip install --user -e git+https://github.com/getting-things-gnome/liblarch.git#egg=liblarch
	pip install --user pytest pycairo PyGObject caldav lxml
	- name: Build and install GTG
	run: \|
	meson setup --prefix=${PWD}/inst ./build
	cd build
	meson compile
	sudo meson install
	- name: Run unit tests with Pytest
	run: \|
	export PYTHONPATH=${PWD}/inst/lib/python3.8/site-packages
	pytest

Provide feedback