Exception generating new chunk - btu cannot be cast to bty

---- Minecraft Crash Report ----
// Don't be sad, have a hug! <3

Time: 1/19/19 8:45 PM
Description: Exception generating new chunk

java.lang.ClassCastException: btu cannot be cast to bty
	at bvz.a(SourceFile:54)
	at bvz.a(SourceFile:17)
	at bva.a(SourceFile:36)
	at cbq.a(SourceFile:85)
	at cbq$$Lambda$2494/1226810481.accept(Unknown Source)
	at java.util.stream.Streams$StreamBuilderImpl.forEachRemaining(Streams.java:419)
	at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
	at cbq.a(SourceFile:84)
	at cas.a(SourceFile:35)
	at bvi.a(SourceFile:20)
	at bvi.a(SourceFile:13)
	at bva.a(SourceFile:36)
	at bdh.a(SourceFile:391)
	at brx.a(SourceFile:125)
	at bsb.c(SourceFile:65)
	at bsb$$Lambda$1023/1004826012.doWork(Unknown Source)
	at bsb$c.doWork(SourceFile:226)
	at bsb.a(SourceFile:189)
	at ue.a(SourceFile:316)
	at ue$$Lambda$2187/1943437964.apply(Unknown Source)
	at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
	at ue.a(SourceFile:310)
	at ue$$Lambda$2152/434514257.apply(Unknown Source)
	at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
	at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
	at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
	at ug.b(SourceFile:57)
	at ug$$Lambda$2186/2114721019.run(Unknown Source)
	at afg.f(SourceFile:83)
	at afg.a(SourceFile:123)
	at afg.run(SourceFile:91)
	at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1689)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Server thread
Stacktrace:
	at bvz.a(SourceFile:54)
	at bvz.a(SourceFile:17)
	at bva.a(SourceFile:36)
	at cbq.a(SourceFile:85)
	at cbq$$Lambda$2494/1226810481.accept(Unknown Source)
	at java.util.stream.Streams$StreamBuilderImpl.forEachRemaining(Streams.java:419)
	at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
	at cbq.a(SourceFile:84)
	at cas.a(SourceFile:35)
	at bvi.a(SourceFile:20)
	at bvi.a(SourceFile:13)
	at bva.a(SourceFile:36)
	at bdh.a(SourceFile:391)
	at brx.a(SourceFile:125)
	at bsb.c(SourceFile:65)
	at bsb$$Lambda$1023/1004826012.doWork(Unknown Source)
	at bsb$c.doWork(SourceFile:226)
	at bsb.a(SourceFile:189)

-- Chunk to be generated --
Details:
	Location: -12,-138
	Position hash: -588410519564
	Generator: btu@7df03d8e
Stacktrace:
	at ue.a(SourceFile:316)
	at ue$$Lambda$2187/1943437964.apply(Unknown Source)
	at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
	at ue.a(SourceFile:310)
	at ue$$Lambda$2152/434514257.apply(Unknown Source)
	at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
	at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
	at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
	at ug.b(SourceFile:57)
	at ug$$Lambda$2186/2114721019.run(Unknown Source)
	at afg.f(SourceFile:83)
	at afg.a(SourceFile:123)

-- Ticking connection --
Details:
	Connection: ip@ddb40fd
Stacktrace:
	at vk.c(SourceFile:175)
	at net.minecraft.server.MinecraftServer.b(SourceFile:845)
	at net.minecraft.server.MinecraftServer.a(SourceFile:756)
	at drn.a(SourceFile:128)
	at net.minecraft.server.MinecraftServer.run(SourceFile:622)
	at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
	Minecraft Version: 19w03c
	Operating System: Windows 7 (amd64) version 6.1
	Java Version: 1.8.0_51, Oracle Corporation
	Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
	Memory: 849694840 bytes (810 MB) / 1511088128 bytes (1441 MB) up to 8482586624 bytes (8089 MB)
	JVM Flags: 7 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx8G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn1G
	Player Count: 1 / 8; [ut['RacinanteOpus'/182, l='190w3c', x=-112.02, y=94.69, z=-2129.51]]
	Data Packs: vanilla
	Type: Integrated Server (map_client.txt)
	Is Modded: Probably not. Jar signature remains and both client + server brands are untouched.