runAtEntityLater method broken on Paper only

[PikaMug]

Thank you for adding c720ba1471f9f60946ce7689d496a229df56b1e8 it works great on Folia!

However, it seems to have broken on Paper, with or without a fallback parameter. FoliaLib 0.3.3 executes the consumer, whereas 0.3.4 simply does not. Furthermore, if a fallback runnable is specified, that gets triggered instead (tested with ProjectileLaunchEvent where the fallback is triggered immediately on launching a Fireball via Player#launchProjectile).

Edit: It appears the Projectile#isValid check returns false on Paper? Perhaps #isDead would be preferable?

Java 17 with Paper version git-Paper-370 (MC: 1.20.4) (Implementing API version 1.20.4-R0.1-SNAPSHOT) (Git: 1fa48d1)