Killing a player with only numbers in their username provides a glitched "Head"

This issue affects

the obtaining of heads with only numbers (no letters at all) in their username

How this differs from the expected behaviour

It should provide the head of said player with their name and skin

How the issue manifests itself

A genertic steve head with nbt data is given. Take for e.g. the account 932 which gave me the following head: Notice it does not stack with other "Heads" (no nbt data) given from previous hourlies (halloween?)

NBT for this "head":

If needed for further testing, 932 is CallMe0n's alt.