Black boxes around

Put the summary of the bug you're having here
It like a black border that moves with me
What I expected to happen was...:
Describe what you thought should happen here
It should be blue and there is nothing i should load
What actually happened was...:
Describe what happened here
a black box showed up
Steps to Reproduce:
1. do /kill on a flat world
2. face in a straight line
3. move your mouse really fast and it should show up