### 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)

ERR_FAIL_COND(!windows.has(p_id));
	WindowData &wd = windows[p_id];
	popup_open(p_id);
	if (p_id != MAIN_WINDOW_ID) {
		_update_window_style(p_id);
	}
	if (wd.maximized) {
		ShowWindow(wd.hWnd, SW_SHOWMAXIMIZED);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	} else if (wd.minimized) {
		ShowWindow(wd.hWnd, SW_SHOWMINIMIZED);
	} else if (wd.no_focus || wd.is_popup) {
		
		ShowWindow(wd.hWnd, SW_SHOWNA);
	} else {
		ShowWindow(wd.hWnd, SW_SHOW);
		SetForegroundWindow(wd.hWnd); 
		SetFocus(wd.hWnd); 
	}
	if (wd.always_on_top) {
		SetWindowPos(wd.hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_FRAMECHANGED | SWP_NOMOVE | SWP_NOSIZE | ((wd.no_focus || wd.is_popup) ? SWP_NOACTIVATE : 0));
	}
}
void DisplayServerWindows::delete_sub_window(WindowID p_window) {