Error to Fix (/Party Chat) command error.

[Stainded]

Null:
org.bukkit.command.CommandException: Unhandled exception executing 'party chat' in rip.diamond.practice.util.command.Command$CommandExecutor(party)
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:138) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at org.bukkit.craftbukkit.v1_8_R3.CraftServer.dispatchCommand(CraftServer.java:683) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.PlayerConnection.handleCommand(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.PlayerConnection.a(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.PacketPlayInChat.a(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.PlayerConnectionUtils.lambda$0(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_361]
at net.minecraft.server.v1_8_R3.SystemUtils.a(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at net.minecraft.server.v1_8_R3.MinecraftServer.lambda$2(Unknown Source) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.FutureTask.runAndReset(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) ~[?:1.8.0_361]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) ~[?:1.8.0_361]
at java.lang.Thread.run(Unknown Source) ~[?:1.8.0_361]
Caused by: java.lang.ClassCastException: rip.diamond.practice.Language cannot be cast to java.lang.String
at rip.diamond.practice.Language.convert(Language.java:733) ~[?:?]
at rip.diamond.practice.Language.toString(Language.java:680) ~[?:?]
at rip.diamond.practice.Language.sendMessage(Language.java:714) ~[?:?]
at rip.diamond.practice.party.PartyMember.toggleChat(PartyMember.java:50) ~[?:?]
at rip.diamond.practice.party.command.PartyCommand.execute(PartyCommand.java:85) ~[?:?]
at rip.diamond.practice.util.command.Command$CommandExecutor.execute(Command.java:99) ~[?:?]
at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:134) ~[Server.jar:1.8.8-R0.2-SNAPSHOT]
... 17 more

[GoodestEnglish]

Will be fixed. Next time please use issues instead of discussions.