Just init TemplateSettings

src/Avalonia.Controls/SplitView/SplitView.cs

@@ -136,15 +136,10 @@ namespace Avalonia.Controls
 
         private Panel? _pane;
         private IDisposable? _pointerDisposable;
-        private SplitViewTemplateSettings _templateSettings = null!;
+        private SplitViewTemplateSettings _templateSettings = new SplitViewTemplateSettings();
         private string? _lastDisplayModePseudoclass;
         private string? _lastPlacementPseudoclass;
 
-        public SplitView()
-        {
-            TemplateSettings = new SplitViewTemplateSettings();
-        }
-
         /// <summary>
         /// Gets or sets the length of the pane when in <see cref="SplitViewDisplayMode.CompactOverlay"/> 
         /// or <see cref="SplitViewDisplayMode.CompactInline"/> mode