The exit portal in the end generates at highest block at 0 0 which can make it generate incomplete

The bug

The exit portal in the end generates at the highest block at 0 0 after opening a pre 1.9 world in 1.9 or newer versions. This can cause the portal to be incomplete. Additionally you might end up with end crystals from old end pillars inside it.

How to reproduce

1. Download MC-93185.zip and drag it into .minecraft\saves.
   Set your Render Distance to 11 or above, due MC-137467.
2. Open the world in the latest version (with the new dragon fight).
   → The portal generated at the highest block at 0 0. With this example it generated incomplete, see End portal generating at highest block (17w06a).png.

How to reproduce (naturally generated)

-953538683905638291

/execute in minecraft:the_end run tp @s 0.35 22.00 0.79 379.99 90.00