Negative amplifier potion effects no longer working

Negative amplifier potion effects no longer work on both players and mobs. If you attempt to use a negative amplifier it will default back to an amplifier of 0. Here are a couple of examples:

summon Potion ~ ~ ~ {Potion:{id:splash_potion,Count:1,tag:{CustomPotionEffects:[{Id:25,Amplifier:-1,Duration:200}]}}}

This will no longer make players/monsters hover in the air. Likewise giving it an amplifier of -2 or below won't make players/monsters slowly descend.

summon Potion ~ ~ ~ {Potion:{id:splash_potion,Count:1,tag:{CustomPotionEffects:[{Id:11,Amplifier:-51,Duration:2000}]}}}

This will no longer make players/monsters take 10x more damage.