No longer try to access non-existing registry key in getStartOnLogonScreen

[lukaszgo1]

Link to issue number:

Fix-up of PR #13242
Originally reported by @Stefan-Kliesch-FHP in #13348

Summary of the issue:

getStartOnLogonScreen can fail with UnboundLocalError when the autostart key does not exist.

Description of how this pull request fixes the issue:

If we failed to open autostart key we no longer try to access it.

Testing strategy:

This is pretty hard to test, but based on the exception from this comment I'm pretty confident about this fix.

Known issues with pull request:

None known

Change log entries:

None needed - unreleased regression.

Code Review Checklist:

• Pull Request description:
  • description is up to date
  • change log entries
• Testing:
  • Unit tests
  • System (end to end) tests
  • Manual testing
• API is compatible with existing add-ons.
• Documentation:
  • User Documentation
  • Developer / Technical Documentation
  • Context sensitive help for GUI changes
• UX of all users considered:
  • Speech
  • Braille
  • Low Vision
  • Different web browsers
  • Localization in other languages / culture than English

[lukaszgo1]

This should be added to 2022.1 milestone.

[AppVeyorBot]

• PASS: Translation comments check.
• PASS: Unit tests.
• PASS: Lint check.
• FAIL: System tests. See test results for more information.
• Build (for testing PR): https://ci.appveyor.com/api/buildjobs/9ghi0g066ydaig24/artifacts/output/nvda_snapshot_pr13384-24795,761b8a15.exe

See test results for failed build of commit 761b8a1582

[seanbudd]

Thanks @lukaszgo1