Invisible arrow shield infront of mob head on top of a moss stone wall with a slime infront of it (havent tried any other mobs)

I was testing the new minecraft version and found a bug.
I had a creeper head on top of a moss stone wall two block from a 11 block high, 4 block wide emrald wall, then I was trying to shoot a slime in between the two and the arrow deflected off of nothing. I didn't test with diffrent heads, walls, or mobs to see the exact problem. It is not a huge glitch, but i desided to post it anyway so it is known. I did some testing and made fome screen shots of the setup, and also found that the same thing happens with chests. And I was messing around and saw a zombie, so i shot at it once and it randomly deflected it, is it a new part of the game?