Problem/Bug How do I fix this error?

When I run the command "/sc test" from the plugin StaffChat, this error message appears.

Code:

15.12 19:53:11 [Server] INFO ... 15 more
15.12 19:53:11 [Server] INFO at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at com.connorlinfoot.betterchat.Commands.StaffChatCommand.onCommand(StaffChatCommand.java:46) ~[?:?]
15.12 19:53:11 [Server] INFO Caused by: java.lang.NoSuchMethodError: org.bukkit.Bukkit.getOnlinePlayers()[Lorg/bukkit/entity/Player;
15.12 19:53:11 [Server] INFO at java.lang.Thread.run(Unknown Source) [?:1.8.0_111]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.MinecraftServer.run(MinecraftServer.java:547) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.MinecraftServer.C(MinecraftServer.java:643) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.DedicatedServer.D(DedicatedServer.java:361) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.MinecraftServer.D(MinecraftServer.java:688) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.SystemUtils.a(SourceFile:45) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at java.util.concurrent.FutureTask.run(Unknown Source) [?:1.8.0_111]
15.12 19:53:11 [Server] INFO at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) [?:1.8.0_111]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.PlayerConnectionUtils$1.run(SourceFile:13) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.PacketPlayInChat.a(SourceFile:9) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.PacketPlayInChat.a(SourceFile:37) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.PlayerConnection.a(PlayerConnection.java:1159) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at net.minecraft.server.v1_10_R1.PlayerConnection.handleCommand(PlayerConnection.java:1299) [CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at org.bukkit.craftbukkit.v1_10_R1.CraftServer.dispatchCommand(CraftServer.java:626) ~[CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:140) ~[CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[CraftBukkit.jar:git-Bukkit-709783c]
15.12 19:53:11 [Server] INFO org.bukkit.command.CommandException: Unhandled exception executing command 'sc' in plugin BetterChat v1.1
15.12 19:53:11 [Server] ERROR null
15.12 19:53:11 [Server] INFO SpecialEffectz: sc test

Specifically these one line of code pops out to me:

Code:

15.12 19:53:11 [Server] INFO Caused by: java.lang.NoSuchMethodError: org.bukkit.Bukkit.getOnlinePlayers()[Lorg/bukkit/entity/Player;

What exactly does this mean? Is it a bukkit error, or a plugin error? Sorry, Don't understand these at all, and I would like to know what the cause of this error is, and what I can do to possibly fix it.

Here is a latest.log of me stopping and starting my server, it might give you some information that you need. http://pastebin.com/cWHS69zr

Let me know if you need anything else like plugin list, etc.

All help is appreciated, thanks