### 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)

wc.lpszClassName = L"Engine";
	if (!RegisterClassExW(&wc)) {
		MessageBoxW(nullptr, L"Failed To Register The Window Class.", L"ERROR", MB_OK | MB_ICONEXCLAMATION);
		r_error = ERR_UNAVAILABLE;
		return;
	}
	_register_raw_input_devices(INVALID_WINDOW_ID);
#if defined(VULKAN_ENABLED)
	if (rendering_driver == "vulkan") {
		context_vulkan = memnew(VulkanContextWindows);
		if (context_vulkan->initialize() != OK) {
			memdelete(context_vulkan);
			context_vulkan = nullptr;
			r_error = ERR_UNAVAILABLE;
			return;
		}
	}
#endif
	
#if defined(GLES3_ENABLED)
	if (rendering_driver == "opengl3") {
		GLManager_Windows::ContextType opengl_api_type = GLManager_Windows::GLES_3_0_COMPATIBLE;
		gl_manager = memnew(GLManager_Windows(opengl_api_type));
		if (gl_manager->initialize() != OK) {
			memdelete(gl_manager);
			gl_manager = nullptr;
			r_error = ERR_UNAVAILABLE;
			return;
		}
		RasterizerGLES3::make_current();