Don't present an undefined execution date

[evanmiller]

If a task had e.g. entered a Failed state but had not yet started, the UI would display the current time as the "Run:" time. This is confusing, as a new timestamp appears each time the user hovers.

---

^ Add meaningful description above

Read the Pull Request Guidelines for more information.
In case of fundamental code changes, an Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in a newsfragment file, named {pr_number}.significant.rst or {issue_number}.significant.rst, in newsfragments.

[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/main/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (ruff, mypy and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
• Consider using Breeze environment for testing locally, it's a heavy docker but it ships with a working Airflow and a lot of integrations.
• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
• Please follow ASF Code of Conduct for all communication including (but not limited to) comments on Pull Requests, Mailing list and Slack.
• Be sure to read the Airflow Coding style.
  Apache Airflow is a community-driven project and together we are making it better 🚀.
  In case of doubts contact the developers at:
  Mailing List: dev@airflow.apache.org
  Slack: https://s.apache.org/airflow-slack

[uranusjr]

Hmm, a ti should have an execution date when it is created, and having undefined here seems wrong in the first place. Maybe we should fix the root cause instead of hiding it.

[evanmiller]

Hmm, a ti should have an execution date when it is created, and having undefined here seems wrong in the first place. Maybe we should fix the root cause instead of hiding it.

The root cause may be very complex; this is a simple fix to prevent operator confusion.

[bbovenzi]

We show the execution date in a lot of places though. How does the rest of the UI look like for that task instance?

[evanmiller]

We show the execution date in a lot of places though. How does the rest of the UI look like for that task instance?

Seems OK? I think the formatting issue is that moment(undefined) uses the current time.

[evanmiller]

Bump

[boring-cyborg]

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