### 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)

if (mouse_mode == MOUSE_MODE_CAPTURED || mouse_mode == MOUSE_MODE_CONFINED || mouse_mode == MOUSE_MODE_CONFINED_HIDDEN) {
					RECT crect;
					GetClientRect(window.hWnd, &crect);
					ClientToScreen(window.hWnd, (POINT *)&crect.left);
					ClientToScreen(window.hWnd, (POINT *)&crect.right);
					ClipCursor(&crect);
				}
			}
			
			
			return 0;
		} break;
		case WM_ENTERSIZEMOVE: {
			Input::get_singleton()->release_pressed_events();
			windows[window_id].move_timer_id = SetTimer(windows[window_id].hWnd, 1, USER_TIMER_MINIMUM, (TIMERPROC) nullptr);
		} break;
		case WM_EXITSIZEMOVE: {
			KillTimer(windows[window_id].hWnd, windows[window_id].move_timer_id);
		} break;
		case WM_TIMER: {
			if (wParam == windows[window_id].move_timer_id) {
				_process_key_events();
				if (!Main::is_iterating()) {
					Main::iteration();
				}
			} else if (wParam == windows[window_id].focus_timer_id) {
				_process_activate_event(window_id, windows[window_id].saved_wparam, windows[window_id].saved_lparam);
				KillTimer(windows[window_id].hWnd, wParam);
				windows[window_id].focus_timer_id = 0U;