Thrower name data is carried over from before version 1.13

Steps to reproduce the issue:

1. Run Minecraft 1.12.2 and throw an item onto the ground (creating an item entity with the Thrower String data: playername)

2. Load the world (and chunk) in modern Minecraft (1.21.11) and receive an error in the console log.

Expected result:

No error.

Actual result:

Error.

[13:59:02] [Server thread/WARN]: [erl] Serialization errors:
chunk@[11, 0][1]: Failed to decode value '"chickeneer"' from field 'Thrower': Not a list

Further analysis:

Item entities used to store the Thrower as a player name. Then in the 1.12 -> 1.13 update, Minecraft started storing as UUID L/M version. In looking through the datafixers, I cannot find a datafixer that dropped the old data, or did anything with that data. https://minecraft.wiki/w/Java_Edition_1.13#:~:text=in%20each%20compound.-,thrower,-and

Then in the 1.15.2 -> 1.16 update. There is a data fixer to convert the UUID L/M to the array of 4 Ints. (Data converter 2514) https://minecraft.wiki/w/Java_Edition_1.16#:~:text=now%20much%20darker.-,uuids,-UUIDs%20stored%20in

Hence the issue of being Not a List.

I only discovered and tested with the “Thrower” data point. May affect other data.

By my best figuring. The issue is that the method net.minecraft.util.datafix.fixes.EntityUUIDFix#updateItem is passing on the original name String, instead of removing it completely when it can't convert it to a modern UUID. I would suggest this data simply gets dropped in this Datafixer, since the reported error is going to drop the data at that point anyway - but with a logged error.

Thank you for your time.
-chickeneer