WorldBorder: LOTS of errors: "Could not pass event ChunkUnloadEvent to WorldBorder v1.9.9 (beta)"

First of all, I’m running a 1.14 server and I understand it’s not officially supported. Just figured I should post this error in the case you’re developing for 1.14.

Server version is spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86

When filling the world, I get thousands of instances of the following error:

> [06:58:43] [Server thread/INFO]: [WorldBorder] [Fill] 179 more chunks processed (7729 total, ~32.8%) (free mem: 3048 MB)
> [06:58:44] [Server thread/ERROR]: Could not pass event ChunkUnloadEvent to WorldBorder v1.9.9 (beta)
org.bukkit.event.EventException: null
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:320) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:70) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at org.bukkit.plugin.SimplePluginManager.fireEvent(SimplePluginManager.java:520) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:505) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.PlayerChunkMap.lambda$12(PlayerChunkMap.java:333) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at java.util.concurrent.CompletableFuture.uniAccept(CompletableFuture.java:656) [?:1.8.0_212]
at java.util.concurrent.CompletableFuture$UniAccept.tryFire(CompletableFuture.java:632) [?:1.8.0_212]
at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442) [?:1.8.0_212]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.executeTask(SourceFile:135) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.executeNext(SourceFile:114) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.ChunkProviderServer$a.executeNext(ChunkProviderServer.java:438) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.ChunkProviderServer.runTasks(ChunkProviderServer.java:163) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.MinecraftServer.aW(MinecraftServer.java:905) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.MinecraftServer.executeNext(MinecraftServer.java:889) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.IAsyncTaskHandler.executeAll(SourceFile:99) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.MinecraftServer.sleepForTick(MinecraftServer.java:872) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:806) [spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.NoSuchMethodError: org.bukkit.event.world.ChunkUnloadEvent.setCancelled(Z)V
at com.wimbli.WorldBorder.WBListener.onChunkUnload(WBListener.java:88) ~[?:?]
at sun.reflect.GeneratedMethodAccessor20.invoke(Unknown Source) ~[?:?]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_212]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_212]
at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:316) ~[spigot-1.14-R0.1-SNAPSHOT.jar:git-Spigot-1eece4f-0d76f86]
... 17 more