Crash fixes

Application/MainWindow/Timer.cs

@@ -24,17 +24,18 @@ public partial class MainWindow
     {
         StopTimer();
 
-        _mainTimer.Dispose();
+        _mainTimer?.Dispose();
+        _mainTimer = null;
     }
 
     private void StartTimer()
     {
-        _mainTimer.Start();
+        _mainTimer?.Start();
     }
 
     private void StopTimer()
     {
-        _mainTimer.Stop();
+        _mainTimer?.Stop();
     }
 
     private void HandleMainTimerElapsed(object sender, EventArgs e)

Application/MainWindow/Toolbar.cs

@@ -166,6 +166,12 @@ public partial class MainWindow
 
         // Delete the feed
         _database.SaveChanges(() => _database.Feeds.Remove(feedToDelete));
+
+        // Refresh the database to current settings
+        ResetDatabase();
+
+        // Re-initialize the feed display
+        DisplayFeed();
     }
 
     private void OpenAllFeedItemsOnSinglePage()