### 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)

DisplayServerWindows *ds_win = static_cast<DisplayServerWindows *>(DisplayServer::get_singleton());
	if (ds_win) {
		return ds_win->WndProc(hWnd, uMsg, wParam, lParam);
	} else {
		return DefWindowProcW(hWnd, uMsg, wParam, lParam);
	}
}
void DisplayServerWindows::_process_activate_event(WindowID p_window_id, WPARAM wParam, LPARAM lParam) {