Remove Guard for null culture

Author: jcansdale

src/GitHub.VisualStudio/UI/Views/Controls/RepositoryCloneControl.xaml.cs

@@ -88,8 +88,6 @@ public RepositoryGroupDescription(RepositoryCloneControl owner)
 
             public override object GroupNameFromItem(object item, int level, System.Globalization.CultureInfo culture)
             {
-                Guard.ArgumentNotNull(culture, nameof(culture));
-
                 var repo = item as IRemoteRepositoryModel;
                 var name = repo?.Owner ?? string.Empty;
                 RepositoryGroup group;