Avoid possible 'System.NullReferenceException' in PredicateLambdaExpressionValueFormatter

[vbreuss]

The ExpressionVisitor.Visit method can accept null as node expression (see here (.NET core) or here (.NET Framework 4.8)).

This fixes a Possible 'System.NullReferenceException' in #2450

IMPORTANT

• If the PR touches the public API, the changes have been approved in a separate issue with the "api-approved" label.
• The code complies with the Coding Guidelines for C#.
• The changes are covered by unit tests which follow the Arrange-Act-Assert syntax and the naming conventions such as is used in these tests.
• If the PR adds a feature or fixes a bug, please update the release notes with a functional description that explains what the change means to consumers of this library, which are published on the website.
• If the PR changes the public API the changes needs to be included by running AcceptApiChanges.ps1 or AcceptApiChanges.sh.
• If the PR affects the documentation, please include your changes in this pull request so the documentation will appear on the website.
  • Please also run ./build.sh --target spellcheck or .\build.ps1 --target spellcheck before pushing and check the good outcome

[github-actions]

Qodana for .NET

It seems all right 👌

No new problems were found according to the checks applied

💡 Qodana analysis was run in the pull request mode: only the changed files were checked

View the detailed Qodana report

To be able to view the detailed Qodana report, you can either:

1. Register at Qodana Cloud and configure the action
2. Use GitHub Code Scanning with Qodana
3. Host Qodana report at GitHub Pages
4. Inspect and use qodana.sarif.json (see the Qodana SARIF format for details)

To get *.log files or any other Qodana artifacts, run the action with upload-result option set to true,
so that the action will upload the files as the job artifacts:

      - name: 'Qodana Scan'
        uses: JetBrains/qodana-action@v2023.2.8
        with:
          upload-result: true

Contact Qodana team

Contact us at qodana-support@jetbrains.com

• Or via our issue tracker: https://jb.gg/qodana-issue
• Or share your feedback: https://jb.gg/qodana-discussions

[coveralls]

Pull Request Test Coverage Report for Build 6846695462

Warning: This coverage report may be inaccurate.

We've detected an issue with your CI configuration that might affect the accuracy of this pull request's coverage report.
To ensure accuracy in future PRs, please see these guidelines.
A quick fix for this PR: rebase it; your next report should be accurate.

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.444%

---

Totals
Change from base Build 6834887943:	0.0%
Covered Lines:	11741
Relevant Lines:	11926

---

💛 - Coveralls

[dennisdoomen]

Although we would love to get test coverage, I don't care enough to bother. But maybe Jonas has a different opinion.