leaves strangely spread outside the old world

I have created an old world with a certain seed (No. seed exist in the picture) when i enter the world Wright blocks spread after the borders of the world (behind the barrier), but when it focuses its leaves! (Oak leaves and in some places the jungle leaves ...)
i can touch The closest to the world and I can break it and I can infield arrows in the leaves near and far

This problem exists in other seeds

Hey strange that if you go out of the world and to enter several times the leaves disappear... its still bug even if it disappear.