The logic in place to prevent players from processing a damage
tick/knockback/etc when hit with 0 damage incorrectly used the damage
events final damage value, which is reduced by absorption.
Instead, use the event's "raw damage", e.g. the amount passed to hurt,
in order to determine if the damage tick should be skipped.
This still allows plugins to change the damage to a non-zero value and
properly damage ticks the player in such a case, but correctly processes
the damage tick in cases where the original damage is non zero but the
actual damage is.