Command Error

19:43:27 [SEVERE] com.sk89q.minecraft.util.commands.WrappedCommandException: jav
a.lang.NullPointerException
19:43:27 [SEVERE]       at com.sk89q.minecraft.util.commands.CommandsManager.inv
okeMethod(CommandsManager.java:532)
19:43:27 [SEVERE]       at com.sk89q.minecraft.util.commands.CommandsManager.exe
cuteMethod(CommandsManager.java:509)
19:43:27 [SEVERE]       at com.sk89q.minecraft.util.commands.CommandsManager.exe
cute(CommandsManager.java:409)
19:43:27 [SEVERE]       at net.roguedraco.rankuponkills.RankupOnKillsPlugin.onCo
mmand(RankupOnKillsPlugin.java:153)
19:43:27 [SEVERE]       at org.bukkit.command.PluginCommand.execute(PluginComman
d.java:40)
19:43:27 [SEVERE]       at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCo
mmandMap.java:168)
19:43:27 [SEVERE]       at org.bukkit.craftbukkit.CraftServer.dispatchCommand(Cr
aftServer.java:492)
19:43:27 [SEVERE]       at net.minecraft.server.NetServerHandler.handleCommand(N
etServerHandler.java:880)
19:43:27 [SEVERE]       at net.minecraft.server.NetServerHandler.chat(NetServerH
andler.java:826)
19:43:27 [SEVERE]       at net.minecraft.server.NetServerHandler.a(NetServerHand
ler.java:808)
19:43:27 [SEVERE]       at net.minecraft.server.Packet3Chat.handle(Packet3Chat.j
ava:44)
19:43:27 [SEVERE]       at net.minecraft.server.NetworkManager.b(NetworkManager.
java:276)
19:43:27 [SEVERE]       at net.minecraft.server.NetServerHandler.d(NetServerHand
ler.java:109)
19:43:27 [SEVERE]       at net.minecraft.server.ServerConnection.b(SourceFile:35
)
19:43:27 [SEVERE]       at net.minecraft.server.DedicatedServerConnection.b(Sour
ceFile:30)
19:43:27 [SEVERE]       at net.minecraft.server.MinecraftServer.q(MinecraftServe
r.java:578)
19:43:27 [SEVERE]       at net.minecraft.server.DedicatedServer.q(DedicatedServe
r.java:213)
19:43:27 [SEVERE]       at net.minecraft.server.MinecraftServer.p(MinecraftServe
r.java:474)
19:43:27 [SEVERE]       at net.minecraft.server.MinecraftServer.run(MinecraftSer
ver.java:406)
19:43:27 [SEVERE]       at net.minecraft.server.ThreadServerApplication.run(Sour
ceFile:539)
19:43:27 [SEVERE] Caused by: java.lang.NullPointerException
19:43:27 [SEVERE]       at net.roguedraco.rankuponkills.Ranks.getNextRank(Ranks.
java:18)
19:43:27 [SEVERE]       at net.roguedraco.rankuponkills.commands.GeneralCommands
.runRankStat(GeneralCommands.java:34)
19:43:27 [SEVERE]       at net.roguedraco.rankuponkills.commands.GeneralCommands
.rankstat(GeneralCommands.java:29)
19:43:27 [SEVERE]       at sun.reflect.NativeMethodAccessorImpl.invoke0(Native M
ethod)
19:43:27 [SEVERE]       at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown S
ource)
19:43:27 [SEVERE]       at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unkno
wn Source)
19:43:27 [SEVERE]       at java.lang.reflect.Method.invoke(Unknown Source)
19:43:27 [SEVERE]       at com.sk89q.minecraft.util.commands.CommandsManager.inv
okeMethod(CommandsManager.java:522)
19:43:27 [SEVERE]       ... 19 more
>