Upstream has released updates that appears to apply and compile correctly.
This update has been tested to ensure that World Conversion still occurs correctly.
Bukkit Changes:
0812ce2c SPIGOT-4397: isChunkGenerated API
CraftBukkit Changes:
4824655c SPIGOT-4398: Upgrade to ASM 6.2.1 for better Java 11 support
eea43870 MC-134115: Fix issues converting tile entities
1a7f2d10 SPIGOT-4397: isChunkGenerated API
40aed54d SPIGOT-4396: Improve vehicle movement
Spigot Changes:
f6a273b1 Rebuild patches
This branch/commit is only useful to those who purely use a clean Bukkit/Spigot/Paper API
and does not use NMS/OBC references.
This will let you start updating your plugin to the latest 1.13 builds of Bukkit Preview (4 as of now)
Note that this release is not final!!! API breakages may occur!
It is up to you if you find use out of this work.