Game crashes when loading a custom biome / java.lang.UnsupportedOperationException: Trying to add tag of type 8 to list of 10

I tried making a village structure feature that can be any type of village and whenever I tried to generate a world with it the game crashed (crash report below).

To reproduce

1. In the create world screen, add the attached datapack (Crashy biome for 1.16.2-pre1.zip).

2. Set the world type to Single Biome with the manossef:multi-village biome selected.

3. Create the world.

4. Watch the world load until it suddenly says "Saving world" and crashes (at least that's what happened to me).

Stack trace

20w28a: crash-2020-07-14_16.11.09-server.txt

Description: Exception generating new chunk

java.lang.IllegalArgumentException: bound must be positive
	at java.util.Random.nextInt(Random.java:388)
	at cqy.a(SourceFile:132)
	at cqs.a(SourceFile:259)
	at cmk$a.a(SourceFile:47)
	at cmk$a.a(SourceFile:33)
	at cnn.a(SourceFile:259)
	at cli.a(SourceFile:34)
	at cik.a(SourceFile:268)
	at cik.a(SourceFile:259)
	at cim.d(SourceFile:51)
	at cim$$Lambda$1615/1511303361.doWork(Unknown Source)
	at cim.a(SourceFile:219)
	at acm.a(SourceFile:568)
	at acm$$Lambda$4134/835142573.apply(Unknown Source)
	at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
	at acm.a(SourceFile:562)
	at acm$$Lambda$4131/1148772743.apply(Unknown Source)
	at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
	at java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
	at java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
	at aco.b(SourceFile:58)
	at aco$$Lambda$4072/113387727.run(Unknown Source)
	at aqs.e(SourceFile:94)
	at aqs.a(SourceFile:137)
	at aqs.run(SourceFile:105)
	at java.util.concurrent.ForkJoinTask$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)

1.16.2-pre1: crash-2020-08-01_11.50.19-server.txt

Description: Starting integrated server

java.lang.UnsupportedOperationException: Trying to add tag of type 8 to list of 10
	at mi.c(SourceFile:254)
	at mi.add(SourceFile:19)
	at java.util.AbstractList.add(AbstractList.java:108)
	at mn.a(SourceFile:169)
	at mn$$Lambda$3975/2030318015.accept(Unknown Source)
	at com.google.common.collect.ImmutableList.forEach(ImmutableList.java:408)
	at mn.a(SourceFile:169)
	at mn.a(SourceFile:196)
	at mn.mergeToList(SourceFile:26)
	at com.mojang.serialization.ListBuilder$Builder.lambda$build$3(ListBuilder.java:74)
	at com.mojang.serialization.ListBuilder$Builder$$Lambda$3973/304581916.apply(Unknown Source)
	at com.mojang.serialization.DataResult.lambda$flatMap$10(DataResult.java:138)
	at com.mojang.serialization.DataResult$$Lambda$648/1532216261.apply(Unknown Source)
	at com.mojang.datafixers.util.Either$Left.map(Either.java:38)
	at com.mojang.serialization.DataResult.flatMap(DataResult.java:136)
	at com.mojang.serialization.ListBuilder$Builder.build(ListBuilder.java:74)
	at com.mojang.serialization.codecs.ListCodec.encode(ListCodec.java:34)
	at com.mojang.serialization.codecs.ListCodec.encode(ListCodec.java:19)
	at com.mojang.serialization.Codec$2.encode(Codec.java:76)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.FieldEncoder.encode(FieldEncoder.java:24)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.codecs.RecordCodecBuilder$Instance$8.encode(RecordCodecBuilder.java:379)
	at com.mojang.serialization.codecs.RecordCodecBuilder$2.encode(RecordCodecBuilder.java:112)
	at com.mojang.serialization.codecs.RecordCodecBuilder$Instance$8.encode(RecordCodecBuilder.java:377)
	at com.mojang.serialization.codecs.RecordCodecBuilder$2.encode(RecordCodecBuilder.java:112)
	at com.mojang.serialization.MapCodec$MapCodecCodec.encode(MapCodec.java:96)
	at vg.a(SourceFile:35)
	at ve.a(SourceFile:27)
	at ve.encode(SourceFile:11)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.FieldEncoder.encode(FieldEncoder.java:24)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.MapEncoder$1.encode(MapEncoder.java:26)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.MapCodec$2.encode(MapCodec.java:68)
	at com.mojang.serialization.codecs.KeyDispatchCodec.encode(KeyDispatchCodec.java:92)
	at com.mojang.serialization.MapCodec$MapCodecCodec.encode(MapCodec.java:96)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.FieldEncoder.encode(FieldEncoder.java:24)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.codecs.RecordCodecBuilder$Instance$6.encode(RecordCodecBuilder.java:295)
	at com.mojang.serialization.codecs.RecordCodecBuilder$2.encode(RecordCodecBuilder.java:112)
	at com.mojang.serialization.codecs.KeyDispatchCodec.encode(KeyDispatchCodec.java:92)
	at com.mojang.serialization.MapCodec$MapCodecCodec.encode(MapCodec.java:96)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.FieldEncoder.encode(FieldEncoder.java:24)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.codecs.RecordCodecBuilder$Instance$4.encode(RecordCodecBuilder.java:223)
	at com.mojang.serialization.codecs.RecordCodecBuilder$2.encode(RecordCodecBuilder.java:112)
	at com.mojang.serialization.MapCodec$MapCodecCodec.encode(MapCodec.java:96)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.BaseMapCodec.encode(BaseMapCodec.java:52)
	at com.mojang.serialization.codecs.UnboundedMapCodec.encode(UnboundedMapCodec.java:43)
	at com.mojang.serialization.codecs.UnboundedMapCodec.encode(UnboundedMapCodec.java:17)
	at com.mojang.serialization.Encoder$1.encode(Encoder.java:25)
	at com.mojang.serialization.Codec$2.encode(Codec.java:76)
	at vd.a(SourceFile:28)
	at vd.encode(SourceFile:11)
	at com.mojang.serialization.Encoder$1.encode(Encoder.java:25)
	at com.mojang.serialization.Codec$2.encode(Codec.java:76)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at com.mojang.serialization.codecs.FieldEncoder.encode(FieldEncoder.java:24)
	at com.mojang.serialization.MapCodec$1.encode(MapCodec.java:39)
	at com.mojang.serialization.codecs.RecordCodecBuilder$Instance$6.encode(RecordCodecBuilder.java:296)
	at com.mojang.serialization.codecs.RecordCodecBuilder$2.encode(RecordCodecBuilder.java:112)
	at com.mojang.serialization.MapCodec$MapCodecCodec.encode(MapCodec.java:96)
	at com.mojang.serialization.Encoder$1.encode(Encoder.java:25)
	at com.mojang.serialization.Codec$2.encode(Codec.java:76)
	at com.mojang.serialization.Encoder.encodeStart(Encoder.java:14)
	at cyf.a(SourceFile:250)
	at cyf.a(SourceFile:231)
	at cya$a.a(SourceFile:339)
	at cya$a.a(SourceFile:333)
	at djt.a(SourceFile:1782)
	at djt.a(SourceFile:1697)
	at dru.p(SourceFile:298)
	at dru.b(SourceFile:238)
	at dru$$Lambda$3117/1181220160.onPress(Unknown Source)
	at dld.b(SourceFile:33)
	at dkx.a(SourceFile:16)
	at dlb.a(SourceFile:149)
	at dmb.a(SourceFile:27)
	at dju.b(SourceFile:92)
	at dju$$Lambda$2990/1075996770.run(Unknown Source)
	at don.a(SourceFile:435)
	at dju.a(SourceFile:92)
	at dju.c(SourceFile:162)
	at dju$$Lambda$2989/1461724962.run(Unknown Source)
	at anw.execute(SourceFile:94)
	at dju.b(SourceFile:162)
	at dju$$Lambda$2343/1658789646.invoke(Unknown Source)
	at org.lwjgl.glfw.GLFWMouseButtonCallbackI.callback(GLFWMouseButtonCallbackI.java:36)
	at org.lwjgl.system.JNI.invokeV(Native Method)
	at org.lwjgl.glfw.GLFW.glfwWaitEventsTimeout(GLFW.java:3174)
	at com.mojang.blaze3d.systems.RenderSystem.limitDisplayFPS(SourceFile:127)
	at djt.e(SourceFile:1043)
	at djt.e(SourceFile:653)
	at net.minecraft.client.main.Main.main(SourceFile:215)