Fixed blinking caret (#12846)

Co-authored-by: Herman Kirshin <herman.kirshin@jetbrains.com>

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -97,7 +97,6 @@ namespace Avalonia.Controls.Presenters
         public TextPresenter()
         {
             _caretTimer = new DispatcherTimer { Interval = TimeSpan.FromMilliseconds(500) };
-            _caretTimer.Tick += CaretTimerTick;
         }
 
         public event EventHandler? CaretBoundsChanged;
@@ -814,6 +813,13 @@ namespace Avalonia.Controls.Presenters
             return _caretBounds;
         }
 
+        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnAttachedToVisualTree(e);
+
+            _caretTimer.Tick += CaretTimerTick;
+        }
+
         protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromVisualTree(e);