BUG: NullReferenceException in QueryTextBox_KeyUp during rapid Dialog Jump input (2.1.3)

[Zubpub]

Description

Flow Launcher 2.1.3 threw an unhandled NullReferenceException in MainWindow.QueryTextBox_KeyUp while its query box was receiving rapid keyboard input during a Save As / Dialog Jump workflow.

This happened during a repeated keyboard-only stress test:

1. Open a native Save As dialog.
2. Open Flow through Dialog Jump.
3. Focus QueryTextBox through Windows UI Automation.
4. Send Ctrl+A, type a folder query, wait about 700 ms, then press Enter.
5. Repeat across consecutive Save As dialogs.

The exception appeared once during the 15-session run. The external helper did not write directly to Flow's internal state; it focused the query control and sent normal keyboard input. That timing may nevertheless be relevant to reproducing the race.

Expected behavior

The query key-up handler should tolerate the result/query state changing during rapid focus and keyboard transitions.

Actual behavior

Flow displayed an unhandled exception and the stress run stopped progressing.

Environment

• Flow Launcher: 2.1.3
• Windows: 10.0.19045.7417
• Process: x64
• IntPtr length: 8
• Python: PythonEmbeddable-v3.11.4\pythonw.exe
• Node path: empty
• Time: 2026-07-14 00:56:34 +08:00

Exception

System.NullReferenceException: Object reference not set to an instance of an object.
   at Flow.Launcher.MainWindow.QueryTextBox_KeyUp(Object sender, KeyEventArgs e) in C:\projects\flow-launcher\Flow.Launcher\MainWindow.xaml.cs:line 1422
   at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
   at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
   at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
   at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
   at System.Windows.Input.InputManager.ProcessStagingArea()
   at System.Windows.Interop.HwndKeyboardInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawKeyboardActions actions, Int32 scanCode, Boolean isExtendedKey, Boolean isSystemKey, Int32 virtualKey)
   at System.Windows.Interop.HwndKeyboardInputProvider.ProcessKeyAction(MSG& msg, Boolean& handled)
   at System.Windows.Interop.HwndSource.CriticalTranslateAccelerator(MSG& msg, ModifierKeys modifiers)
   at System.Windows.Interop.HwndSource.OnPreprocessMessage(Object param)
   at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
   at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)

The corresponding log file is Flow.Launcher.2026-07-14.log (147,668 bytes).