Console Error HELP

On Console when i reload Mythic mobs i get these error:

18.02 18:14:18 [Server] WARN Exception in thread "Craft Scheduler Thread - 286" 18.02 18:14:18 [Server] WARN org.apache.commons.lang.UnhandledException: Plugin MythicMobs v4.0.0 generated an exception while executing task 604

18.02 18:14:33 [Server] WARN Exception in thread "Craft Scheduler Thread - 254" 18.02 18:14:33 [Server] WARN org.apache.commons.lang.UnhandledException: Plugin MythicMobs v4.0.0 generated an exception while...

Console Error HELP