Use a nil pointer if entry is "" #27

	name: dockerfile

	on:
	workflow_dispatch:
	push:
	tags:
	- 'v*'
	pull_request:
	branches: [ master ]

	jobs:
	dockerfile:
	name: Run Dockerfiles in examples
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2

	- name: Run example - simple
	run: \|
	docker build -t simple -f ./_example/simple/Dockerfile .
	docker run simple \| grep 99\ こんにちは世界099

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