Alt + F4 will crash the program

[orzFly]

In the Wox window, press Alt+F4 will crash.

   在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
   在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
   在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
   在 Wox.EntryPoint.Main(String[] args) 位置 C:\Projects\Wox\Wox\App.xaml.cs:行号 20
   在 System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
   在 System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   在 System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   在 System.Threading.ThreadHelper.ThreadStart()

[Rovak]

Changing this to return false; seems to fix the issue for me, but i doubt that is the "right" way to fix it.

I suppose that SingleInstanceManager tries to refer the MainForm property on shutdown, which is not set, which triggers an error.