When you add a data value to items with durability that have the "Unbreakable" nbt data tag it comes up as a missing texture. I've seen previous posts about this, but now that we can add textures for each data value, we need to be able to hide the durability bar. So before you resolve this saying "Just use data value 0", remember that with the 1.9 texture update it would be extremely helpful if we could hide the durability bar while using that new feature.
You know what would work even better? An NBT tag for hiding the durability bar. Could be as easy as "DurabilityBar:0" for off and "DurabilityBar:1" for on...