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Duplicate of MC-84253 – If you have not, please use the search function in the future, to see if your bug has already been submitted.

Duplicate of MC-84253 – If you have not, please use the search function in the future, to see if your bug has already been submitted.

That isn't a bug
I think U can go to this page .

Duplicate of MC-84253 – If you have not, please use the search function in the future, to see if your bug has already been submitted.

But when I made a world in 'a' it spawn automatically.
Or I just wrong?

But how about the "Create New World" issue?

Oh, and after clicked the "Delete World" button it won't deleted and I still can hear a skeleton from the main menu.

EnderCrystal isn't a block dude, they're entity.
U can summon EnderCrystal using command "/summon EnderCrystal"