minor fix

Author: mou-haz

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

@@ -543,7 +543,7 @@ private static void OnFocusVisualIsVisibleChanged(object sender, DependencyPrope
         private static void ApplyCornerRadiusToFocusVisual(Control focusVisual, FrameworkElement focusedElement, Thickness focusVisualMargin)
         {
             var cornerRadius = GetCornerRadiusForFocusedElement(focusedElement);
-            if (cornerRadius is CornerRadius focusedCornerRadius)
+            if (cornerRadius is CornerRadius focusedCornerRadius && focusedCornerRadius != default)
             {
                 var focusVisualCornerRadius = new CornerRadius(
                     GetSumIfSourceIsNonZero(focusedCornerRadius.TopLeft, -(focusVisualMargin.Left + focusVisualMargin.Top) / 2),
@@ -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
             };