The Bug:

Sniffers ignore the "minecraft:generic.movement_speed" attribute.

Steps to Reproduce:

1. Summon a sniffer with its "minecraft:generic.movement_speed" attribute set to a value of "0" by using the command provided below.

   /summon minecraft:sniffer ~ ~ ~ {Attributes:[{Base:0.0d,Name:"generic.movement_speed"}]}

2. Wait for the sniffer to begin wandering around.
3. Take note as to whether or not sniffers ignore the "minecraft:generic.movement_speed" attribute.

Observed Behavior:

Sniffers ignore the "minecraft:generic.movement_speed" attribute.

Expected Behavior:

Sniffers would not ignore the "minecraft:generic.movement_speed" attribute.

Code Analysis:

Code analysis by Tis_awesomeness can be found in this comment.