### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Windows 11 22H2

### Issue description

If a focused subwindow is destroyed, DisplayServerWindows may still attempt to send mouse motion events to that window, because `last_focused_window` isn't updated until another window is focused.

```
ERROR: Condition "!windows.has(p_window)" is true. Returning: Point2i()
   at: window_get_position (platform/windows/display_server_windows.cpp:999)
```

### Steps to reproduce

Run the MRP, click some non-Godot application window to focus it, then click the "CLOSE" button in the secondary window. This destroys the window without re-focusing the main window, so hovering the mouse over the main window will produce the error message above.

### Minimal reproduction project

[native_windows_hover.zip](https://github.com/godotengine/godot/files/10573386/native_windows_hover.zip)

SetPriorityClass(GetCurrentProcess(), ABOVE_NORMAL_PRIORITY_CLASS);
		DWORD index = 0;
		HANDLE handle = AvSetMmThreadCharacteristicsW(L"Games", &index);
		if (handle) {
			AvSetMmThreadPriority(handle, AVRT_PRIORITY_CRITICAL);
		}
		
		
		SetThreadPriority(GetCurrentThread(), THREAD_PRIORITY_TIME_CRITICAL);
	}
	cursor_shape = CURSOR_ARROW;
	_update_real_mouse_position(MAIN_WINDOW_ID);
	r_error = OK;
	static_cast<OS_Windows *>(OS::get_singleton())->set_main_window(windows[MAIN_WINDOW_ID].hWnd);
	Input::get_singleton()->set_event_dispatch_function(_dispatch_input_events);
}
Vector<String> DisplayServerWindows::get_rendering_drivers_func() {
	Vector<String> drivers;
#ifdef VULKAN_ENABLED
	drivers.push_back("vulkan");
#endif
#ifdef GLES3_ENABLED
	drivers.push_back("opengl3");
#endif
	return drivers;
}
DisplayServer *DisplayServerWindows::create_func(const String &p_rendering_driver, WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Vector2i *p_position, const Vector2i &p_resolution, int p_screen, Error &r_error) {