### 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)

mm->set_alt_pressed(alt_mem);
			mm->set_button_mask(last_button_state);
			POINT coords; 
			coords.x = GET_X_LPARAM(lParam);
			coords.y = GET_Y_LPARAM(lParam);
			ScreenToClient(windows[window_id].hWnd, &coords);
			mm->set_position(Vector2(coords.x, coords.y));
			mm->set_global_position(Vector2(coords.x, coords.y));
			if (mouse_mode == MOUSE_MODE_CAPTURED) {
				Point2i c(windows[window_id].width / 2, windows[window_id].height / 2);
				old_x = c.x;
				old_y = c.y;
				if (mm->get_position() == c) {
					center = c;
					return 0;
				}
				Point2i ncenter = mm->get_position();
				center = ncenter;
				POINT pos = { (int)c.x, (int)c.y };
				ClientToScreen(hWnd, &pos);
				SetCursorPos(pos.x, pos.y);
			}
			mm->set_velocity(Input::get_singleton()->get_last_mouse_velocity());
			if (old_invalid) {
				old_x = mm->get_position().x;
				old_y = mm->get_position().y;
				old_invalid = false;
			}
			mm->set_relative(Vector2(mm->get_position() - Vector2(old_x, old_y)));
			old_x = mm->get_position().x;