java.util.ConcurrentModificationException
    at java.util.WeakHashMap$HashIterator.nextEntry(WeakHashMap.java:806)
    at java.util.WeakHashMap$KeyIterator.next(WeakHashMap.java:839)
    at net.minecraftforge.common.FarmlandWaterManager.removeTickets(FarmlandWaterManager.java:127)
    at net.minecraftforge.common.ForgeInternalHandler.onChunkUnload(ForgeInternalHandler.java:104)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_448_ForgeInternalHandler_onChunkUnload_Unload.invoke(.dynamic)
    at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
    at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:746)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostChunkUnloadEvent(SpongeToForgeEventFactory.java:992)
    at org.spongepowered.mod.event.SpongeToForgeEventFactory.createAndPostForgeEvent(SpongeToForgeEventFactory.java:291)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:338)
    at org.spongepowered.mod.event.SpongeModEventManager.extendedPost(SpongeModEventManager.java:435)
    at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:404)
    at org.spongepowered.common.event.SpongeEventManager.post(SpongeEventManager.java:465)
    at org.spongepowered.common.SpongeImpl.postEvent(SpongeImpl.java:246)
    at net.minecraft.world.chunk.Chunk.handler$onUnload$zlm000(Chunk.java:1936)
    at net.minecraft.world.chunk.Chunk.onUnload(Chunk.java:880)
    at net.minecraft.world.gen.ChunkProviderServer.tick(ChunkProviderServer.java:800)
    at net.minecraft.world.WorldServer.tick(WorldServer.java:207)
    at net.minecraft.server.MinecraftServer.updateTimeLightAndEntities(MinecraftServer.java:756)
    at net.minecraft.server.dedicated.DedicatedServer.updateTimeLightAndEntities(DedicatedServer.java:397)
    at net.minecraft.server.MinecraftServer.tick(MinecraftServer.java:668)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526)
    at java.lang.Thread.run(Thread.java:748)