优化代码

Ink Canvas/MainWindow_cs/MW_PPT.cs

@@ -100,7 +100,6 @@ namespace Ink_Canvas
         // 页面切换防抖机制
         private DateTime _lastSlideSwitchTime = DateTime.MinValue;
         private int _pendingSlideIndex = -1;
-        private System.Timers.Timer _slideSwitchDebounceTimer;
         private const int SlideSwitchDebounceMs = 150;
         private bool _isInkClearedByButton = false;
         #endregion

Ink Canvas/Windows/TimerControl.xaml.cs

@@ -1294,7 +1294,7 @@ namespace Ink_Canvas.Windows
                     recentTimer6 = "--:--";
                 }
             }
-            catch (Exception ex)
+            catch (Exception)
             {
                 recentTimer1 = "--:--";
                 recentTimer2 = "--:--";