fix #325 - null simple keys not properly nullified #125

	name: D

	on:
	push:
	branches: [ master ]
	pull_request:
	branches: [ master ]

	jobs:
	build:
	strategy:
	matrix:
	dc:
	- dmd-latest
	- ldc-latest
	- dmd-beta
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v3
	with:
	fetch-depth: 2
	- uses: dlang-community/setup-dlang@v1
	with:
	compiler: ${{ matrix.dc }}
	- name: 'Test'
	run: \|
	dub test -c unittest-dip1000
	dub test --build=unittest-cov
	bash <(curl -s https://codecov.io/bash)
	examples:
	runs-on: ubuntu-latest
	needs: build
	steps:
	- uses: actions/checkout@v3
	- uses: dlang-community/setup-dlang@v1
	with:
	compiler: dmd-latest
	- name: 'Build Examples'
	run: \|
	dub build dyaml:benchmark
	dub build dyaml:constructor
	dub build dyaml:getting-started
	dub build dyaml:representer
	dub build dyaml:resolver
	dub build dyaml:testsuite
	dub build dyaml:tojson
	dub build dyaml:tokens
	dub build dyaml:yaml_gen
	dub build dyaml:yaml_stats
	ninja:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v3
	- uses: dlang-community/setup-dlang@v1
	with:
	compiler: dmd-latest
	- name: 'Install dependencies'
	run: \|
	sudo apt-get install python3-pip python3-setuptools python3-wheel ninja-build
	sudo pip3 install meson
	- name: 'Build'
	run: \|
	export PATH=$PATH:$PWD/.ntmp
	meson build && ninja -j8 -C build
	ninja -j8 -C build test -v
	yaml-test-suite:
	runs-on: ubuntu-latest
	needs: build
	steps:
	- uses: actions/checkout@v3
	- uses: dlang-community/setup-dlang@v1
	with:
	compiler: dmd-latest
	- name: 'Run YAML test suite'
	run: \|
	git clone https://github.com/yaml/yaml-test-suite
	dub run dyaml:testsuite

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