"[SEVERE] Item entity # has no item?" is spammed in the console and items appear as stone for invalid IDs or on initial drop

The Server is spammed with Item entity number has no item!? until it crashes. ~~It is the spawners because it stops when i break them. The spawners are custom and spawn armour and weapons. A copy of the spawner is in the attachments and a crash report.

Confirmed for 13w41b with the following command, in a command block:

/setblock ~ ~1 ~ minecraft:mob_spawner 1 replace {EntityId:Item,SpawnData:{Health:5,Age:0,Item:{id:7,Damage:0,Count:1}}}

Observe the spam in the Development Console of the launcher, or the server console if you perform this on a server.

The message is now of the form:

Client> [02:10:41] [Client thread/ERROR]: Item entity 9740 has no item?!

Marcono says:

Like I wrote already, the problem is the getEntityItem() method (MCP 1.8 name). Minecraft expects it to be null when no item data is stored but this method is required to return an ItemStack for rendering (else the client will crash). Because of this currently it returns a new ItemStack if the stored ItemStack is null (and prints the "Item entity # has not item?!" error message).