add test case where `json_str` is set to `None` #36

	name: Build PyDataverse
	on: [push]

	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	python-version: ["3.8", "3.9", "3.10", "3.11"]
	name: Build pyDataverse
	steps:
	- name: "Checkout"
	uses: "actions/checkout@v4"
	- name: Setup Python
	uses: actions/setup-python@v3
	with:
	python-version: ${{ matrix.python-version }}
	- name: Install Python Dependencies
	run: \|
	python3 -m pip install --upgrade pip
	python3 -m pip install poetry

	poetry install

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