Minecolonies version

Current version on the server

Actual behaviour

[16:30:19] [Server thread/ERROR]: Failed to save chunkjava.util.ConcurrentModificationException at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1211) ~[?:1.8.0_92] at java.util.TreeMap$KeyIterator.next(TreeMap.java:1265) ~[?:1.8.0_92] at net.minecraft.world.WorldServer.func_175712_a(WorldServer.java:664) ~[le.class:?] at net.minecraft.world.WorldServer.func_72920_a(WorldServer.java:642) ~[le.class:?] at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75820_a(AnvilChunkLoader.java:380) ~[anj.class:?] at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75816_a(AnvilChunkLoader.java:165) [anj.class:?] at net.minecraft.world.gen.ChunkProviderServer.func_73242_b(ChunkProviderServer.java:238) [ld.class:?] at net.minecraft.world.gen.ChunkProviderServer.func_73156_b(ChunkProviderServer.java:339) [ld.class:?] at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:203) [le.class:?] at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:690) [MinecraftServer.class:?] at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:344) [ko.class:?] at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:605) [MinecraftServer.class:?] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:481) [MinecraftServer.class:?] at java.lang.Thread.run(Thread.java:745) [?:1.8.0_92]

on hiring a worker.