Bukkit

What steps will reproduce the problem?
1.Run on 1.9 and wait in console for error

What is the expected output? What do you see instead?
Nothing is expected I get...
[17:48:46 WARN]: org.apache.commons.lang.UnhandledException: Plugin MirrorMaster v1.21 generated an exception while executing task 39
    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 be.mc.woutwoot.MirrorMaster.MetricsLite.postPlugin(MetricsLite.java:285)
    at be.mc.woutwoot.MirrorMaster.MetricsLite.access$3(MetricsLite.java:278)
    at be.mc.woutwoot.MirrorMaster.MetricsLite$1.run(MetricsLite.java:173)
    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
What version of the product are you using?
The latest

Do you have an error log of what happened?
It is above.

Plugin works great other than that and an occasional bit of lag.