Avoid crashing when Bluetooth adapter is not available

[TimoPtr]

Summary

While working on the #7035 I found out that we are currently crashing the app when the device doesn't have a Bluetooth adapter which could happen. This PR handle this case.

Checklist

• New or updated tests have been added to cover the changes following the testing guidelines.
• The code follows the project's code style and best_practices.
• The changes have been thoroughly tested, and edge cases have been considered.
• Changes are backward compatible whenever feasible. Any breaking changes are documented in the changelog for users and/or in the code for developers depending on the relevance.
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[Copilot]

Pull request overview

This PR prevents crashes in the Improv (BLE Wi‑Fi onboarding) integration on devices that do not have a Bluetooth adapter by making Improv manager creation nullable and ensuring scan/provision flows don’t dereference a missing adapter.

Changes:

• Make ImprovManagerFactory return ImprovManager? and return null when no Bluetooth adapter is present.
• Update ImprovRepositoryImpl to tolerate a missing Improv manager during scanning and teardown, and to short-circuit provisioning when the manager is unavailable.
• Add unit tests covering the “no Bluetooth adapter” behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
app/src/main/kotlin/io/homeassistant/companion/android/frontend/improv/ImprovRepositoryImpl.kt	Handles ImprovManager being nullable to avoid crashes and make scan/stopScan safe when no adapter exists.
app/src/main/kotlin/io/homeassistant/companion/android/frontend/improv/ImprovManagerFactory.kt	Updates the factory contract to allow returning null on devices without a Bluetooth adapter.
app/src/main/kotlin/io/homeassistant/companion/android/frontend/improv/FrontendImprovModule.kt	Adjusts the Hilt-provided factory to only create ImprovManager when a Bluetooth adapter is available.
app/src/test/kotlin/io/homeassistant/companion/android/frontend/improv/ImprovRepositoryImplTest.kt	Adds tests for missing-adapter cases (scan/provision).

[jpelgrom]

While this is a good additional check, these calls should never happen from the frontend if there is no Bluetooth adapter because then the device should be sending canSetupImprov = false, preventing the frontend from interacting with the app's Improv implementation. Did you check if the config sends this correctly / there is a frontend issue here as well?

[TimoPtr]

While this is a good additional check, these calls should never happen from the frontend if there is no Bluetooth adapter because then the device should be sending canSetupImprov = false, preventing the frontend from interacting with the app's Improv implementation. Did you check if the config sends this correctly / there is a frontend issue here as well?

The issue was on hilt side, since we inject the manager into the ViewModel and the ImprovManager is in a class attribute it was initiated when created. In the initialization there is an attribute that get the Bluetooth adapter without checking if it's available and causing a NPE.

[jpelgrom]

OK that would have been good context to have and obvious if a stacktrace was included :)

Checked the library and indeed we're using the adapter without additional checks. The user (= this app) is supposed to handle permission/availability checks.