Fix Crashlytics symbol upload default guard

[AdamEssenmacher]

Summary

• correct the Crashlytics symbol-upload default guard to check the property it assigns
• preserve an explicit value supplied before the NuGet props import

Validation

• verified a pre-set False value remains False in Release
• verified an unset Release value defaults to True
• verified an unset Debug value remains empty
• ran dotnet tool run dotnet-cake -- --target=nuget --names=Firebase.Crashlytics successfully with zero warnings and errors
• confirmed the corrected props file is present under both build and buildTransitive in the generated package

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T17:49:43.261824Z	0c251f1	PR opened

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