[windows][installer] fix crash on update

[AenBleidd]

Summary by cubic

Fixes a Windows installer crash during updates by safely handling empty registry strings in the custom action.

• Bug Fixes
  • Guard against empty values before trimming the trailing null in BOINCCABase::GetRegistryValue.
  • Added SetupStateRestored_Set_Empty_Registry_Values unit test to ensure no crash and correct defaults when registry values are empty.

^{Written for commit c33cbb8. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

_{Re-trigger cubic}

[Copilot]

Pull request overview

This PR addresses a Windows installer update crash in the boinccas custom action by making BOINCCABase::GetRegistryValue resilient to zero-length registry data, and adds a regression test to ensure empty registry values don’t crash the restore-setup-state path.

Changes:

• Guard strValue.back() with an emptiness check before trimming a trailing '\0' in BOINCCABase::GetRegistryValue.
• Add a unit test covering the “setup state stored + registry values present but empty” scenario and asserting expected defaults/outputs.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
clientsetup/win/boinccas.cpp	Prevents a crash by avoiding .back() on an empty registry value buffer before trimming a trailing null.
tests/unit-tests/boinccas/test_boinccas_CARestoreSetupState.cpp	Adds regression coverage for empty registry values during setup-state restore, validating no crash and correct property defaults.

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