Fixed item frames do not take void damage

Item frames that have the "Fixed" data tag set to 1b do not take damage when placed below y -64.

Reproduction:

1. Spawn an item frame with the Fixed tag set to 1, and give it an entity tag to test with.
   /summon item_frame ~ ~ ~ {Fixed:1b,Tags:[test]}
2. Teleport the item frame to any y coordinate below -64.
   /teleport @e[type=item_frame,tag=test] ~ -70 ~
3. Execute as the item frame to ensure that it still exists.
   /execute as @e[type=item_frame,tag=test] run say test