null
org.bukkit.command.CommandException: Unhandled exception executing command 'friendsgui' in plugin PartyAndFriendsGUI v1.0.19
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[PluginCommand.class:git-Cauldron-MCPC-Plus-1.7.10-1.1236.05.210]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:181) ~[SimpleCommandMap.class:git-Cauldron-MCPC-Plus-1.7.10-1.1236.05.210]
        at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchCommand(CraftServer.java:717) ~[CraftServer.class:git-Cauldron-MCPC-Plus-1.7.10-1.1236.05.210]
        at net.minecraft.network.NetHandlerPlayServer.func_147361_d(NetHandlerPlayServer.java:1350) [nh.class:?]
        at net.minecraft.network.NetHandlerPlayServer.func_147354_a(NetHandlerPlayServer.java:1132) [nh.class:?]
        at net.minecraft.network.play.client.C01PacketChatMessage.func_148833_a(C01PacketChatMessage.java:38) [ir.class:?]
        at net.minecraft.network.play.client.C01PacketChatMessage.func_148833_a(C01PacketChatMessage.java:53) [ir.class:?]
        at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:244) [ej.class:?]
        at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:173) [nc.class:?]
        at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:980) [MinecraftServer.class:?]
        at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:423) [lt.class:?]
        at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:798) [MinecraftServer.class:?]
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:658) [MinecraftServer.class:?]
        at java.lang.Thread.run(Thread.java:745) [?:1.8.0_66]
Caused by: java.lang.NoClassDefFoundError: de/simonsator/partyandfriendsgui/api/PartyFriendsAPI
        at de.simonsator.partyandfriendsgui.main.Main.onCommand(Main.java:80) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[PluginCommand.class:git-Cauldron-MCPC-Plus-1.7.10-1.1236.05.210]
        ... 13 more