Fix issues in registry checks

[Sharparam]

## Description

Fixes some null reference issues in the registry helper as well as adding support for the new "Apps" subkey, under which the "Enable" flag can be found in newer SDK versions.

Motivation and Context

On fresh installations of the SDK, calls to IsSdkEnabled have started failing due to the changes in registry structure.

How Has This Been Tested?

Tested locally, modifying the registry to see how it behaves.

Types of changes

• [X] Bug fix (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 change)

Checklist:

• [X] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [X] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes where applicable.
• [X] All new and existing tests passed.

Fixes #288.

[AppVeyorBot]

:white_check_mark: Build Colore 6.0.1-beta.2.build.234 completed (commit https://github.com/chroma-sdk/Colore/commit/4272bc501c by @Sharparam)