Fix TypeError when deserializing task with execution_timeout set to None

[wjszlachta-man]

This fixes a bug where task deserialisation fails with TypeError when task execution_timeout is set to None, but core.default-task-execution-timeout is not set to None in airflow.cfg.

In order to reproduce:

• set core.default-task-execution-timeout in airflow.cfg to any integer value
• set execution_timeout=None on any operator inside a DAG
• open DAG in Airflow UI
• you will see Internal Server Error in the browser, and the following in webserver logs:

...
airflow/serialization/serialized_objects.py:1488: in deserialize_operator
    cls.populate_operator(op, encoded_op)
airflow/serialization/serialized_objects.py:1345: in populate_operator
    v = cls._deserialize_timedelta(v)
airflow/serialization/serialized_objects.py:941: in _deserialize_timedelta
    return datetime.timedelta(seconds=seconds)
E   TypeError: unsupported type for timedelta seconds component: NoneType

If you are running with scheduler.standalone-dag-processor set to True, this is more catastrophic as you will see the same deserialization error in scheduler and you will not be able to schedule any new tasks.

---

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[boring-cyborg]

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[boring-cyborg]

Awesome work, congrats on your first merged pull request! You are invited to check our Issue Tracker for additional contributions.

[github-actions]

Backport failed to create: v2-10-test. View the failure log Run details

Status	Branch	Result
❌	v2-10-test

You can attempt to backport this manually by running:

cherry_picker 97d62ee v2-10-test

This should apply the commit to the v2-10-test branch and leave the commit in conflict state marking
the files that need manual conflict resolution.

After you have resolved the conflicts, you can continue the backport process by running:

cherry_picker --continue

[potiuk]

backported to v2-10-test