plotme error

[17:36:00] [Craft Scheduler Thread - 2/WARN]: Exception in thread "Craft Scheduler Thread - 2"
[17:36:00] [Craft Scheduler Thread - 2/WARN]: org.apache.commons.lang.UnhandledException: Plugin PlotMe v0.13g generated an exception while executing task 59
	at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.util.ConcurrentModificationException
	at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
	at java.util.HashMap$KeyIterator.next(Unknown Source)
	at com.worldcretornica.plotme.PlayerList.replace(PlayerList.java:114)
	at com.worldcretornica.plotme.PlotManager$2.run(PlotManager.java:1678)
	at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftTask.run(CraftTask.java:71)
	at org.bukkit.craftbukkit.v1_7_R4.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
	... 3 more

[17:36:00] [Craft Scheduler Thread - 1/INFO]: Finished fetching 0 UUIDs. Starting database update.