So, basically, if you use the command /give @p diamond_helmet 1 1 {Unbreakable:1}, it'll give you the item, but with the missing texture texture. This works for all armor types.
So, basically, if you use the command /give @p diamond_helmet 1 1 {Unbreakable:1}, it'll give you the item, but with the missing texture texture. This works for all armor types.
You're giving yourself a diamond helmet with a damage value of 1, which is meant to give an invalid texture by default. For it to work properly, set the damage value to 0.