Fix null exception

Author: Jack251970

Flow.Launcher/ViewModel/MainViewModel.cs

@@ -1333,7 +1333,10 @@ private static List<Result> GetHistoryItems(IEnumerable<HistoryItem> historyItem
 
         private async Task QueryResultsAsync(bool searchDelay, bool isReQuery = false, bool reSelect = true)
         {
-            await _updateSource?.CancelAsync();
+            if (_updateSource != null)
+            {
+                await _updateSource.CancelAsync();
+            }
             _progressQuery = null;
 
             App.API.LogDebug(ClassName, $"Start query with text: <{QueryText}>");
@@ -1927,7 +1930,10 @@ public async Task SetupDialogJumpAsync(nint handle)
             if (DialogJump.DialogJumpWindowPosition == DialogJumpWindowPositions.UnderDialog)
             {
                 // Cancel the previous Dialog Jump task
-                await _dialogJumpSource?.CancelAsync();
+                if (_dialogJumpSource != null)
+                {
+                    await _dialogJumpSource.CancelAsync();
+                }
 
                 // Create a new cancellation token source
                 _dialogJumpSource = new CancellationTokenSource();