### 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)

IDC_SIZEWE,
		IDC_HELP
	};
	if (cursors_cache.has(p_shape)) {
		SetCursor(cursors[p_shape]);
	} else {
		SetCursor(LoadCursor(hInstance, win_cursors[p_shape]));
	}
	cursor_shape = p_shape;
}
DisplayServer::CursorShape DisplayServerWindows::cursor_get_shape() const {
	return cursor_shape;
}
void DisplayServerWindows::cursor_set_custom_image(const Ref<Resource> &p_cursor, CursorShape p_shape, const Vector2 &p_hotspot) {
	_THREAD_SAFE_METHOD_
	if (p_cursor.is_valid()) {
		RBMap<CursorShape, Vector<Variant>>::Element *cursor_c = cursors_cache.find(p_shape);
		if (cursor_c) {
			if (cursor_c->get()[0] == p_cursor && cursor_c->get()[1] == p_hotspot) {
				cursor_set_shape(p_shape);
				return;
			}
			cursors_cache.erase(p_shape);
		}
		Ref<Texture2D> texture = p_cursor;
		Ref<AtlasTexture> atlas_texture = p_cursor;
		Ref<Image> image;
		Size2 texture_size;
		Rect2 atlas_rect;
		if (texture.is_valid()) {