I've noticed today on my iPhone 7 that there is a small gap between the screen assembly and the metal back at the top of the phone. It's wide enough that dust collects in there and that I can slide a sheet of paper a few millimetres in there. However, the sides and bottom of the phone don't have this gap, and I can't get a sheet of paper in between. I spoke to a friend who also bought a 7 on the same day and he says his one is the same. Is this normal? Do any of you readers have it as well? Most importantly, will it affect the water resistance?