I was enchanting books and applying enchants to my armor when all the other outlines of other armor slots in my survival inventory disappeared after I placed my enchanted diamond helmet on its slot, but it reappeared every time I wasn't pointing at the helmet. The same with chestplate, but only the outlines in the leggings and boots slot disappeared. I tried using unenchanted armor and no problems – only when enchanted helmet/chestplate in their slots is pointed at.