### 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)

}
			touch_state.clear();
			bool self_steal = false;
			HWND new_hwnd = (HWND)wParam;
			if (IsWindow(new_hwnd)) {
				self_steal = true;
			}
			if (!self_steal) {
				if (OS::get_singleton()->get_main_loop()) {
					OS::get_singleton()->get_main_loop()->notification(MainLoop::NOTIFICATION_APPLICATION_FOCUS_OUT);
				}
				app_focused = false;
			}
		} break;
		case WM_ACTIVATE: { 
			if (!windows[window_id].window_focused) {
				_process_activate_event(window_id, wParam, lParam);
			} else {
				windows[window_id].saved_wparam = wParam;
				windows[window_id].saved_lparam = lParam;
				
				windows[window_id].focus_timer_id = SetTimer(windows[window_id].hWnd, 2, USER_TIMER_MINIMUM, (TIMERPROC) nullptr);
			}
			if (wParam != WA_INACTIVE) {
				track_mouse_leave_event(hWnd);
			}
			return 0; 
		} break;
		case WM_GETMINMAXINFO: {
			if (windows[window_id].resizable && !windows[window_id].fullscreen) {