when exception occurs - backup crash and after no more save are done

[Kervinou]

[16:00:46] [Craft Scheduler Thread - 1350/WARN]: Exception in thread "Craft Scheduler Thread - 1350"
[16:00:46] [Craft Scheduler Thread - 1350/WARN]: org.apache.commons.lang.UnhandledException: Plugin Backup v2.5 generated an exception while executing task 10
at org.bukkit.craftbukkit.v1_7_R2.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:724)
Caused by: java.util.ConcurrentModificationException
at org.bukkit.craftbukkit.v1_7_R2.util.LongObjectHashMap$ValueIterator.next(LongObjectHashMap.java:314)
at net.minecraft.server.v1_7_R2.ChunkProviderServer.saveChunks(ChunkProviderServer.java:284)
at net.minecraft.server.v1_7_R2.WorldServer.save(WorldServer.java:802)
at org.bukkit.craftbukkit.v1_7_R2.CraftWorld.save(CraftWorld.java:672)
at com.bukkitbackup.full.threading.PrepareBackup.prepareBackup(PrepareBackup.java:128)
at com.bukkitbackup.full.threading.PrepareBackup.checkShouldDoBackup(PrepareBackup.java:96)
at com.bukkitbackup.full.threading.PrepareBackup.run(PrepareBackup.java:42)
at org.bukkit.craftbukkit.v1_7_R2.scheduler.CraftTask.run(CraftTask.java:58)
at org.bukkit.craftbukkit.v1_7_R2.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
... 3 more