Upstream has released updates that appear 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:
33a2b476 PR-734: Make PlayerInventory#getItem Nullable
CraftBukkit Changes:
953d3ddc SPIGOT-3034: PlayerKickEvent.setLeaveMessage(String) doesn't actually do anything
2c47af0c SPIGOT-6963: CraftMetaBlockState#getBlockState applied TileEntity ids without the minecraft namespace prefix.
Jake Potrebic
Nassim Jahnke
Jason Penilla