1.5.2 crash

2016-01-30 23:30:05 [SEVERE] java.util.ConcurrentModificationException
2016-01-30 23:30:05 [SEVERE] 	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
2016-01-30 23:30:05 [SEVERE] 	at java.util.HashMap$ValueIterator.next(Unknown Source)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75820_a(AnvilChunkLoader.java:419)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75816_a(AnvilChunkLoader.java:215)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.world.gen.ChunkProviderServer.func_73242_b(ChunkProviderServer.java:345)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.world.gen.ChunkProviderServer.func_73151_a(ChunkProviderServer.java:422)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.world.WorldServer.func_73044_a(WorldServer.java:1187)
2016-01-30 23:30:05 [SEVERE] 	at org.bukkit.craftbukkit.v1_5_R3.CraftWorld.save(CraftWorld.java:774)
2016-01-30 23:30:05 [SEVERE] 	at org.bukkit.command.defaults.SaveCommand.execute(SaveCommand.java:30)
2016-01-30 23:30:05 [SEVERE] 	at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:189)
2016-01-30 23:30:05 [SEVERE] 	at org.bukkit.craftbukkit.v1_5_R3.CraftServer.dispatchCommand(CraftServer.java:555)
2016-01-30 23:30:05 [SEVERE] 	at org.bukkit.craftbukkit.v1_5_R3.CraftServer.dispatchServerCommand(CraftServer.java:538)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.server.dedicated.DedicatedServer.func_71333_ah(DedicatedServer.java:364)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:321)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:732)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:614)
2016-01-30 23:30:05 [SEVERE] 	at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:573)