Fix crash on setting string.Empty in SettingsCard

Author: Dub1shu

components/SettingsControls/src/SettingsCard/SettingsCard.cs

@@ -247,20 +247,20 @@ private void OnDescriptionChanged()
     {
         if (GetTemplateChild(DescriptionPresenter) is FrameworkElement descriptionPresenter)
         {
-            descriptionPresenter.Visibility = Description != null
-                ? Visibility.Visible
-                : Visibility.Collapsed;
+            descriptionPresenter.Visibility = IsNullOrEmptyString(Description)
+                ? Visibility.Collapsed
+                : Visibility.Visible;
         }
-    
+
     }
 
     private void OnHeaderChanged()
     {
         if (GetTemplateChild(HeaderPresenter) is FrameworkElement headerPresenter)
         {
-            headerPresenter.Visibility = Header != null
-                ? Visibility.Visible
-                : Visibility.Collapsed;
+            headerPresenter.Visibility = IsNullOrEmptyString(Header)
+                ? Visibility.Collapsed
+                : Visibility.Visible;
         }
 
     }
@@ -274,7 +274,7 @@ private void CheckVerticalSpacingState(VisualState s)
     {
         // On state change, checking if the Content should be wrapped (e.g. when the card is made smaller or the ContentAlignment is set to Vertical). If the Content and the Header or Description are not null, we add spacing between the Content and the Header/Description.
 
-        if (s != null && (s.Name == RightWrappedState || s.Name == RightWrappedNoIconState || s.Name == VerticalState) && (Content != null) && (Header != null || Description != null))
+        if (s != null && (s.Name == RightWrappedState || s.Name == RightWrappedNoIconState || s.Name == VerticalState) && (Content != null) && (!IsNullOrEmptyString(Header) || !IsNullOrEmptyString(Description)))
         {
             VisualStateManager.GoToState(this, ContentSpacingState, true);
         }
@@ -295,4 +295,19 @@ private void CheckVerticalSpacingState(VisualState s)
             return FocusManager.GetFocusedElement() as FrameworkElement;
         }
     }
+
+    private static bool IsNullOrEmptyString(object obj)
+    {
+        if (obj == null)
+        {
+            return true;
+        }
+
+        if (obj is string objString && objString == string.Empty)
+        {
+            return true;
+        }
+
+        return false;
+    }
 }