Question [1.21.6] Prevent Nether Portal destroying

[Erfinderlabyrinth]

How can I prevent Nether portals from being destroyed, even if the frame is broken?
I tried the following, but it didn't work:

    @EventHandler
    public void onPortalPhysics(BlockPhysicsEvent event) {
        if (event.getBlock().getType() == Material.NETHER_PORTAL || event.getChangedType() == Material.NETHER_PORTAL) {
            System.out.println("Cancel");
            event.setCancelled(true);
        }
    }