The bug
The death message "death.attack.witherSkull.item" is untranslated.
How to reproduce
Use a command to summon a wither that is holding a renamed item.
/summon wither ~ ~ ~ {HandItems:[{id:stone,Count:1b,tag:{display:{Name:"\"test\""}}}]}
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)
Switch to survival mode.
Let the wither's skulls hit you and kill you.
Look at the death message.
Attachments
Comments 18
I have attached a resource pack that works around both this bug and another related one known as MC-186687. It does so by adding a translation string for death.attack.witherSkull.item and replacing that of death.attack.witherSkull to fit for all entities.
@Kathy McGill now that I looked into the Minecraft code I am sure there is no other death message. The last one nobody knows about is "death.attack.dryout", which fish are supposed to get when they die out of the water, but there is no way of making this appear.
[^Wither Skull Messages [1.16+].zip]