Game crash when putting an item in the offhand of an entity with attack slots

Trying to use commands to give an entity with attack slots an item in their offhand will cause a crash.

Reproduction Steps

1. Summon any entity that has attack slots with /summon, in chat, or by using a spawn egg.
2. Type in chat: "/replaceitem entity @e[type=minecraft:<insert entity id here>, c=1] slot.weapon.offhand -106 <insert item id here>