Bukkit

What steps will reproduce the problem?
1.Start server (Spigot 1.9)
2.look at the end of startup log
3.

What is the expected output? What do you see instead?
How can I fix this?

What version of the product are you using?
PermissionsBukkit v2.5

Do you have an error log of what happened?
[04:48:33 WARN]: Exception in thread "Craft Scheduler Thread - 3"
[04:48:33 WARN]: org.apache.commons.lang.UnhandledException: Plugin PermissionsBukkit v2.5 generated an exception while executing task 33
at org.bukkit.craftbukkit.v1_9_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NoSuchMethodError: org.bukkit.Server.getOnlinePlayers()[Lorg/bukkit/entity/Player; at org.mcstats.Metrics.postPlugin(Metrics.java:357)
at org.mcstats.Metrics.access$400(Metrics.java:64) at org.mcstats.Metrics$1.run(Metrics.java:245)
at org.bukkit.craftbukkit.v1_9_R1.scheduler.CraftTask.run(CraftTask.java:71)
at org.bukkit.craftbukkit.v1_9_R1.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53) ... 3 more [04:48:33 WARN]: Exception in thread "Craft Scheduler Thread - 14"

Please provide any additional information below.
It works fine but it spam the console. 2 others plugins have exactly the same error: LWC and Antipub.
If it's a server-side problem, how can I know the origin of the problem?