Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
e461dcfe #555: Item - add getters/setters for owner/thrower
CraftBukkit Changes:
055870c4 #758: Item - add getters/setters for owner/thrower
The maps did convert successfully, but had noisy logs due to Spigot
implementing this logic incorrectly.
This stops the spam by converting the old format to new before
requesting the world.