minor fix

Author: mou-haz

source/iNKORE.UI.WPF.Modern/Controls/Helpers/FocusVisualHelper.cs

@@ -567,7 +567,7 @@ private static void ApplyCornerRadiusToFocusVisual(Control focusVisual, Framewor
             cornerRadiusTarget ??= focusedElement;
             return cornerRadiusTarget switch
             {
-                var _ when cornerRadiusTarget.GetValue(Border.CornerRadiusProperty) is CornerRadius borderResult => borderResult,
+                var _ when cornerRadiusTarget.GetValue(Border.CornerRadiusProperty) is CornerRadius borderResult && borderResult != default => borderResult,
                 var _ when cornerRadiusTarget.GetValue(ControlHelper.CornerRadiusProperty) is CornerRadius controlResult => controlResult,
                 _ => null
             };