### 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)

case WINDOW_FLAG_TRANSPARENT: {
			return wd.layered_window;
		} break;
		case WINDOW_FLAG_NO_FOCUS: {
			return wd.no_focus;
		} break;
		case WINDOW_FLAG_MOUSE_PASSTHROUGH: {
			return wd.mpass;
		} break;
		case WINDOW_FLAG_POPUP: {
			return wd.is_popup;
		} break;
		default:
			break;
	}
	return false;
}
void DisplayServerWindows::window_request_attention(WindowID p_window) {
	_THREAD_SAFE_METHOD_
	ERR_FAIL_COND(!windows.has(p_window));
	const WindowData &wd = windows[p_window];
	FLASHWINFO info;
	info.cbSize = sizeof(FLASHWINFO);
	info.hwnd = wd.hWnd;
	info.dwFlags = FLASHW_TRAY;
	info.dwTimeout = 0;
	info.uCount = 2;
	FlashWindowEx(&info);
}
void DisplayServerWindows::window_move_to_foreground(WindowID p_window) {