"death.attack.witherSkull.item" displays raw translation string (is untranslated)

The bug

The death message "death.attack.witherSkull.item" is untranslated.

How to reproduce

1. Use a command to summon a wither that is holding a renamed item.

   /summon wither ~ ~ ~ {HandItems:[{id:stone,Count:1b,tag:{display:{Name:"\"test\""}}}]}
   

1. Switch to easy difficulty. (not necessary, but you should make sure that you don't wither away and that you get killed by the wither's skull)
2. Switch to survival mode.
3. Let the wither's skulls hit you and kill you.
4. Look at the death message.