### 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)

_THREAD_SAFE_METHOD_
	ERR_FAIL_COND_V(!windows.has(p_window), Point2i());
	const WindowData &wd = windows[p_window];
	if (wd.minimized) {
		return wd.last_pos;
	}
	RECT r;
	if (GetWindowRect(wd.hWnd, &r)) {
		return Point2i(r.left, r.top) - _get_screens_origin();
	}
	return Point2i();
}
void DisplayServerWindows::_update_real_mouse_position(WindowID p_window) {
	ERR_FAIL_COND(!windows.has(p_window));
	POINT mouse_pos;
	if (GetCursorPos(&mouse_pos) && ScreenToClient(windows[p_window].hWnd, &mouse_pos)) {
		if (mouse_pos.x > 0 && mouse_pos.y > 0 && mouse_pos.x <= windows[p_window].width && mouse_pos.y <= windows[p_window].height) {
			old_x = mouse_pos.x;
			old_y = mouse_pos.y;
			old_invalid = false;
			Input::get_singleton()->set_mouse_position(Point2i(mouse_pos.x, mouse_pos.y));
		}
	}
}
void DisplayServerWindows::window_set_position(const Point2i &p_position, WindowID p_window) {