In some cases 'cancel-workflow-run' action crashes

[potiuk]

In some cases, when the PR is weird - when there is an empty PR that gets closed quickly I guess such as:

https://github.com/apache/airflow/runs/2265280777?check_suite_focus=true,

the 'cancel-workflow-runs' action crashes:

Adding the run: 717090708 to candidates with :1029499:astronomer/airflow:bump-openapi:pull_request key.


Checking run number: 21885 RunId: 717087278 Url: https://api.github.com/repos/apache/airflow/actions/runs/717087278 Status in_progress Created at 2021-04-04T17:25:26Z


Adding the run: 717087278 to candidates with :1029499:apache/airflow:master:push key.


Checking run number: 21884 RunId: 717051432 Url: https://api.github.com/repos/apache/airflow/actions/runs/717051432 Status in_progress Created at 2021-04-04T17:02:39Z

Error: Cannot read property 'full_name' of null

This results in cancelling all other workflows and is an easy way to DDOs airflow. It can be handled by cancelling the offending workflow. This should be handled better

UPDATE: this hppens where "head_repository" is null - which is somewhat error on GitHub side. But still we should handle it better.

Apache Airflow version:

Kubernetes version (if you are using kubernetes) (use kubectl version):

Environment:

• Cloud provider or hardware configuration:
• OS (e.g. from /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
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What happened:

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