Brief Description:
When the slow falling effect is active, you cannot critically damage mobs.

Steps to Reproduce:
1. Give yourself the slow falling effect.
2. Attempt to critically hits mobs.
3. You will notice that you are unable to.

Observed Results:
The mob doesn't take critical damage.

Expected Results:
The mob should take critical damage.

Screenshots/Videos:
I've attached a short video with shows this bug in action.