Handle incomplete Sonos alarm event payloads

[jjlawren]

Proposed change

Sonos speakers can sometimes send incomplete alarm event payloads. This handles those instances.

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

Additional information

• This PR fixes or closes issue: fixes Missing key in Sonos alarm event #51318
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• The code has been formatted using Black (black --fast homeassistant tests)
• Tests have been added to verify that the new code works.

The integration reached or maintains the following Integration Quality Scale:

• No score or internal
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• I have reviewed two other open pull requests in this repository.