black line flickering at the edge of world

i decided to try the new snapshot so i created a new world and entered it to see some of the new banners and check on the fps.

but when i logged in a black line shoved up across the screen wich i will attach a screenshot of in the attachment this line might have something to do with the new block loading
Steps to Reproduce:
i realy don't know how you should reproduce the problem as i do not know why it happened.