What's wrong with this WorldGuard hook?

Hello!
I have an error, when I try to hook WorldGuard with their own api, I get an error :S

Here's the code:
[This line is the error: Plugin plugin = getServer().getPluginManager().getPlugin("WorldGuard");]

Code:java

 
private WorldGuardPlugin getWorldGuard() {
   Plugin plugin = getServer().getPluginManager().getPlugin("WorldGuard");
 
   // WorldGuard may not be loaded
   if (plugin == null || !(plugin instanceof WorldGuardPlugin)) {
       return null; // Maybe you want throw an exception instead
   }
 
   return (WorldGuardPlugin) plugin;
}
 

Error code in console

Code:

10:40:50 [ALLVARLIG] Could not load 'plugins\PearlMan.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NullPointerException
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.j
ava:152)
        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.
java:305)
        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager
.java:230)
        at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:223)
        at org.bukkit.craftbukkit.CraftServer.<init>(CraftServer.java:199)
        at net.minecraft.server.ServerConfigurationManagerAbstract.<init>(Server
ConfigurationManagerAbstract.java:50)
        at net.minecraft.server.ServerConfigurationManager.<init>(SourceFile:11)
 
        at net.minecraft.server.DedicatedServer.init(DedicatedServer.java:105)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:377)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:539)
Caused by: java.lang.NullPointerException
        at com.adde.pearlman.PearlManMain.getWorldGuard(PearlManMain.java:51)
        at com.adde.pearlman.PearlManMain.<init>(PearlManMain.java:62)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
 
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Sou
rce)
        at java.lang.reflect.Constructor.newInstance(Unknown Source)
        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.j
ava:148)
        ... 9 more

 

Code:

Caused by: java.lang.NullPointerException
        at com.adde.pearlman.PearlManMain.getWorldGuard(PearlManMain.java:51)

Line 51 pls

 

this is how you call for worldguard

WorldGuardPlugin wg = (WorldGuardPlugin) Bukkit.getServer().getPluginManager().getPlugin("WorldGuard");
It could also be that you don't have wg in your plugins folder