When crafting alternate patterns in recipe book, item previews are invisible

When I was trying to craft some Dark Oak Signs using the recipe book, I noticed that the item previews for the alternate patterns were invisible. On previous versions, it showed item previews so you knew which you were crafting.

To Reproduce

1. Load version 21w10a
2. Search "sign" in recipe book.
3. Right click sign to check alternate patterns
4. Observe that item previews are missing.
5. Load version 21w08b or lower
6. Do steps 2-3 again
7. Observe that item previews are showing.