Add loading info text when opening scene animation window

Source/Editor/GUI/Timeline/Timeline.cs

@@ -1930,6 +1930,18 @@ namespace FlaxEditor.GUI.Timeline
             }
         }
 
+        /// <summary>
+        /// Sets the text for the No Tracks UI.
+        /// </summary>
+        /// <param name="text">The text.</param>
+        public void SetNoTracksText(string text)
+        {
+            if (_noTracksLabel != null)
+            {
+                _noTracksLabel.Text = text ?? "No tracks";
+            }
+        }
+
         /// <inheritdoc />
         protected override void PerformLayoutBeforeChildren()
         {

Source/Editor/Windows/Assets/SceneAnimationWindow.cs

@@ -632,6 +632,7 @@ namespace FlaxEditor.Windows.Assets
             };
             _timeline.Modified += OnTimelineModified;
             _timeline.PlayerChanged += OnTimelinePlayerChanged;
+            _timeline.SetNoTracksText("Loading...");
 
             // Toolstrip
             _saveButton = (ToolStripButton)_toolstrip.AddButton(Editor.Icons.Save64, Save).LinkTooltip("Save");
@@ -857,6 +858,7 @@ namespace FlaxEditor.Windows.Assets
 
                 // Setup
                 _undo.Clear();
+                _timeline.SetNoTracksText(null);
                 _timeline.Enabled = true;
                 ClearEditedFlag();
             }