[AIRFLOW-6076] fix dag.cli() KeyError

[penggongkui]

fix this issue: https://issues.apache.org/jira/browse/AIRFLOW-6076

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst)
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[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Backport packages$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Backport packages$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[github-actions]

The Workflow run is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Backport packages$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.

[mik-laj]

Can you add tests to avoid regression? Besides, thanks a lot for fixing this bug. This is not the first time we've tried to fix this, but I hope we'll have success this time.

[mik-laj]

CI is green, but it still needs tests.

[penggongkui]

I have added some test cases

CI is green, but it still needs tests.

[penggongkui]

@mik-laj could you please review this PR

how about add this to the 2.0.2 milestone

[boring-cyborg]

Awesome work, congrats on your first merged pull request!