Mannequin entities with an invalid elytra texture specified use the missing texture rather than falling back to the default elytra texture

If a mannequin has an invalid resource location specified for its elytra texture, it will display the missing texture, rather than falling back to the normal texture for elytra as one would expect.

Commands to reproduce:

/summon minecraft:mannequin ~ ~ ~ {profile:{texture:"entity/player/wide/sunny",elytra:"invalidelytratexture"}}

/item replace entity @n[type=minecraft:mannequin] armor.chest with minecraft:elytra

Expected results: the default elytra texture would be used.

Actual results: the missing texture is used, as though the current resource pack is somehow broken.