Do not throw if configuration is empty during report generation

[FabienTschanz]

Pull Request (PR) description

This pull request addresses a reported issue when the configuration to create a report from was empty. Currently, it throws an exception, but that isn't the best solution, especially if multiple reports are being generated, because an exception stops the entire processing of the reports.

The proposed change is to output a warning, stating that the configuration was empty and no report was created. Another way that was suggested is to create an empty report stating something like No configuration found, but that requires additional handling in the create functions for the specific report type.

For visibility:
@andikrueger

This Pull Request (PR) fixes the following issues

• Fixes [ERROR] M365DSCReport.psm1 - New-M365DSCReportFromConfiguration function - Parsed content was null #4505
• Fixes New-M365DSCReportFromConfiguration: parsed content was null #4559

[FabienTschanz]

Note: The Unit tests are failing due to changes in the Dev branch. I will update the PR as soon as that works again.