When teleporting mobs and items to the End, a second platform is created

Summary:
When teleporting items and mobs to the End, a second obsidian platform is created, which is 1 height lower than a regular platform. Mobs and items spawn on the bottom platform (which sometimes causes them to choke) and players on the top platform.

Steps to reproduce:

1. Build an end portal/place end portal block.
2. Throw items at him/teleport mob.
3. Teleport yourself through the portal.
4. See if two obsidian platforms have been created. If not, go to the Overworld and repeat steps 2 and 3.

Observed results:
In the End, two obsidian platforms can be created.

Expected results:
Only one platform should be created in End.