Crash in AppHost::_QuitRequested

[zadjii-msft]

From 1.21 stable crash dumps.

891ec77c-0eb3-2890-9aa6-ed3abd60948b

MSFT:50659255

13.41% of our crashes currently(!)

"INVALID_POINTER_READ_c0000005_WindowsTerminal.exe!winrt::impl::consume_Windows_UI_Xaml_IDependencyObject_winrt::Windows::UI::Xaml::UIElement_::Dispatcher"

terminal/src/cascadia/WindowsTerminal/AppHost.cpp

Lines 1201 to 1227 in e8c1568

	void AppHost::_QuitRequested(const winrt::Windows::Foundation::IInspectable&, const winrt::Windows::Foundation::IInspectable&)
	{
	// We process the shutdown synchronously here, because otherwise the
	// AutomaticShutdownRequested() logic wouldn't run synchronously either.
	til::latch latch{ 1 };
	_windowLogic.GetRoot().Dispatcher().RunAsync(winrt::Windows::UI::Core::CoreDispatcherPriority::Normal, [&latch, weakThis = weak_from_this()]() {
	const auto countDownOnExit = wil::scope_exit([&latch] {
	latch.count_down();
	});
	const auto self = weakThis.lock();
	if (!self)
	{
	return;
	}
	if (self->_appLogic && self->_windowLogic && self->_appLogic.ShouldUsePersistedLayout())
	{
	self->_windowLogic.PersistState();
	}
	PostQuitMessage(0);
	});
	latch.wait();
	}