When using class-level-validation via INotifyDataErrorInfo every entry is shown twice

[timunie]

• .NET Core Version: 5.0.103
• Windows version: 10.0.19042
• Does the bug reproduce also in WPF for .NET Framework 4.8?: Yes
• Is this bug related specifically to tooling in Visual Studio (e.g. XAML Designer, Code editing, etc...)? No
• Security issues and bugs should be reported privately, learn more via our responsible disclosure guidelines.

Problem description:
If you bind to a class which implements INotifyDataErrorInfo it runs validation for the whole class. It should show the issue for each property once, but shows it twice.

Actual behavior:
Every issue is shown twice like shown in the following image:

Investigating this further showed that the method GetErrors(string propertyName) gets calles twice. One time for null and one time for string.Empty. According to the docs both calls will return the same result: https://docs.microsoft.com/en-us/dotnet/api/system.componentmodel.inotifydataerrorinfo.geterrors?view=net-5.0

"The name of the property to retrieve validation errors for; or null or Empty, to retrieve entity-level errors."

I also discussed this here as I first thought it was a bug there: CommunityToolkit/WindowsCommunityToolkit#3763

Expected behavior:
Every issue is shown only once.

Minimal repro:
https:/timunie/MvvmToolkitValidationSample

Thank you and happy coding
Tim