TextBox validation border is not cleared when initial state has a ValidationError

[AsaharaHiroshi]

When using ModernWpf's TextBox with WPF validation (e.g., IDataErrorInfo / validation rules) and disabling the default Validation.ErrorTemplate, the red error border is not cleared after the validation error is resolved if the initial state already has a validation error.

In other words:

• If the binding starts with an invalid value (initial ValidationError),
• the TextBox shows the red error border as expected on load,
• but even after the user enters a valid value and the validation passes, the red border remains visible.

This only happens in the "initial error" scenario. If the control starts in a valid state and then becomes invalid/valid, the border behaves as expected.