Can someone tell me what I did wrong?

OK! So, I'm trying to spawn an NPC with the Citizens API on a chat message. So here's the code with no errors at all:

Code:

                    }else if(message.equalsIgnoreCase("come here ava npc")){
                            NPCManager.register("Ava", player.getLocation(), player.getName(), NPCCreateReason.SPAWN);
                            player.sendMessage("Here I am!");

But when I type that the console comes back with this error:

14:41:11 [INFO] <fellwolfpaw> come here ava npc
14:41:11 [WARNING] Task of 'AvaBot' generated an exception
java.lang.NoClassDefFoundError: net/minecraft/server/Packet17
at net.citizensnpcs.resources.npclib.PathNPC.<init>(PathNPC.java:28)
at net.citizensnpcs.resources.npclib.CraftNPC.<init>(CraftNPC.java:15)
at net.citizensnpcs.resources.npclib.NPCSpawner.spawnNPC(NPCSpawner.java
:31)
at net.citizensnpcs.resources.npclib.NPCManager.register(NPCManager.java
:164)
at net.citizensnpcs.resources.npclib.NPCManager.register(NPCManager.java
:193)
at me.fellwolfpaw.AvaBot.AvaChatBot$1.run(AvaChatBot.java:186)
at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(C
raftScheduler.java:137)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:482)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:457)
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.Packet17
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:36)
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:24)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 10 more>

Any help would be greatly appreciated ^_^ Thanks

 

NoClassDefFoundError - JavaDocs

Check to see if all of your libraries are included when you compile your project.