Add Null Safety

[gcardinale]

Changes :balloon:

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Types of changes

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• [x] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist :heavy_check_mark:

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• [ ] I have read the coding convention guidelines and my code follows these.
• [x] Unit tests pass locally with my changes
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have added necessary documentation (if appropriate)

Further comments

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[fredeil]

Can you explain what this is @gcardinale?

[gcardinale]

Addr compatibility null-safety (flutter >= 2.12.0)

[gcardinale]

Oh but @britannio update thi feature. Exuse Me