Item frame with map on anvil appears transparent where the map hasn't been filled out

Put the summary of the bug you're having here

What I expected to happen was...:
The blank area on the map would be shown

What actually happened was...:
You can see through the blank area on the map to the anvil below

Steps to Reproduce:
1. Partially fill out a map
2. Place an item frame on top of an anvil
3. Place the map in the item frame