Handle case when native_schema is None

[metascroy]

Summary: https://fb.workplace.com/groups/pytorch.edge.users/posts/1714672769403009/?comment_id=1721960698674216

Differential Revision: D71413713

[pytorch-bot]

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❌ 2 New Failures, 1 Pending, 1 Unrelated Failure

As of commit 72b4e08 with merge base 0e5f309 ():

NEW FAILURES - The following jobs have failed:

• Check Labels / Check labels (gh)
  RuntimeError: Error checking labels: PR does not have required labels
• Lint / lintrunner / linux-job (gh)
  >>> Lint for exir/program/_program.py:

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest-arm / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

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[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D71413713

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