> [01:59:22] [Server thread/FATAL] [minecraft/MinecraftServer]: Error executing task
java.util.concurrent.ExecutionException: java.lang.NoClassDefFoundError: net/minecraft/client/multiplayer/WorldClient
at java.util.concurrent.FutureTask.report(FutureTask.java:122) ~[?:1.8.0_212]
at java.util.concurrent.FutureTask.get(FutureTask.java:192) ~[?:1.8.0_212]
at net.minecraft.util.Util.func_181617_a(SourceFile:47) [h.class:?]
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:723) [MinecraftServer.class:?]
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:397) [nz.class:?]
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:668) [MinecraftServer.class:?]
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:526) [MinecraftServer.class:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_212]
Caused by: java.lang.NoClassDefFoundError: net/minecraft/client/multiplayer/WorldClient
at immersiveradialmenu.network.SwapItems.swapItem(SwapItems.java:51) ~[SwapItems.class:?]
at immersiveradialmenu.network.SwapItems$Handler.lambda$onMessage$0(SwapItems.java:71) ~[SwapItems$Handler.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_212]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_212]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
... 5 more
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.multiplayer.WorldClient
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:101) ~[launchwrapper-1.12.jar:?]
at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_212]
at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_212]
at immersiveradialmenu.network.SwapItems.swapItem(SwapItems.java:51) ~[SwapItems.class:?]
at immersiveradialmenu.network.SwapItems$Handler.lambda$onMessage$0(SwapItems.java:71) ~[SwapItems$Handler.class:?]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_212]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[?:1.8.0_212]
at net.minecraft.util.Util.func_181617_a(SourceFile:46) ~[h.class:?]
... 5 more