Fix person device_trackers null

[balloob]

Breaking change

Proposed change

If a person has onboarded before we migrated person integration to the new collection helper, we accidentally had written device_trackers as None. It should always be a list. Some people fixed this for themselves by mutating person via the config UI, for the rest, this will fix it.

This should fix errors people experience with registering a mobile app.

Fixes #31816

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

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# Example configuration.yaml

Additional information

• This PR fixes or closes issue: fixes #
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