### 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)

Point2i offset = _get_screens_origin();
	POINT p;
	p.x = p_position.x + offset.x;
	p.y = p_position.y + offset.y;
	HWND hwnd = WindowFromPoint(p);
	for (const KeyValue<WindowID, WindowData> &E : windows) {
		if (E.value.hWnd == hwnd) {
			return E.key;
		}
	}
	return INVALID_WINDOW_ID;
}
DisplayServer::WindowID DisplayServerWindows::create_sub_window(WindowMode p_mode, VSyncMode p_vsync_mode, uint32_t p_flags, const Rect2i &p_rect) {
	_THREAD_SAFE_METHOD_
	WindowID window_id = _create_window(p_mode, p_vsync_mode, p_flags, p_rect);
	ERR_FAIL_COND_V_MSG(window_id == INVALID_WINDOW_ID, INVALID_WINDOW_ID, "Failed to create sub window.");
	WindowData &wd = windows[window_id];
	if (p_flags & WINDOW_FLAG_RESIZE_DISABLED_BIT) {
		wd.resizable = false;
	}
	if (p_flags & WINDOW_FLAG_BORDERLESS_BIT) {
		wd.borderless = true;
	}
	if (p_flags & WINDOW_FLAG_ALWAYS_ON_TOP_BIT && p_mode != WINDOW_MODE_FULLSCREEN && p_mode != WINDOW_MODE_EXCLUSIVE_FULLSCREEN) {
		wd.always_on_top = true;
	}
	if (p_flags & WINDOW_FLAG_NO_FOCUS_BIT) {