Mod Crashing Server

Hi, When i start a server with my mod it crashes.

here is the crash report:

Encountered an unexpected exception
java.lang.NoClassDefFoundError: net/minecraft/client/model/ModelCreeper
   at mod.mcreator.plus_utilities.(plus_utilities.java:184) ~[modid-1.0.jar:?]
   at java.lang.Class.forName0(Native Method) ~[?:1.8.0_192]
   at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_192]
   at net.minecraftforge.fml.common.FMLModContainer.constructMod(FMLModContainer.java:528) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_192]
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_192]
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_192]
   at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_192]
   at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76) ~[guava-21.0.jar:?]
   at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.EventBus.post(EventBus.java:217) ~[guava-21.0.jar:?]
   at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:218) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:196) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_192]
   at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_192]
   at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_192]
   at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_192]
   at com.google.common.eventbus.Subscriber.invokeSubscriberMethod(Subscriber.java:91) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber$SynchronizedSubscriber.invokeSubscriberMethod(Subscriber.java:150) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber$1.run(Subscriber.java:76) ~[guava-21.0.jar:?]
   at com.google.common.util.concurrent.MoreExecutors$DirectExecutor.execute(MoreExecutors.java:399) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Subscriber.dispatchEvent(Subscriber.java:71) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.Dispatcher$PerThreadQueuedDispatcher.dispatch(Dispatcher.java:116) ~[guava-21.0.jar:?]
   at com.google.common.eventbus.EventBus.post(EventBus.java:217) ~[guava-21.0.jar:?]
   at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:135) ~[LoadController.class:?]
   at net.minecraftforge.fml.common.Loader.loadMods(Loader.java:593) ~[Loader.class:?]
   at net.minecraftforge.fml.server.FMLServerHandler.beginServerLoading(FMLServerHandler.java:98) ~[FMLServerHandler.class:?]
   at net.minecraftforge.fml.common.FMLCommonHandler.onServerStart(FMLCommonHandler.java:333) ~[FMLCommonHandler.class:?]
   at net.minecraft.server.dedicated.DedicatedServer.init(DedicatedServer.java:128) ~[DedicatedServer.class:?]
   at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:552) [MinecraftServer.class:?]
   at java.lang.Thread.run(Thread.java:748) [?:1.8.0_192]
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.model.ModelCreeper
   at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191) ~[launchwrapper-1.12.jar:?]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_192]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_192]
   ... 35 more
Caused by: net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerException: Exception in class transformer net.minecraftforge.fml.common.asm.transformers.SideTransformer@dcc6211 from coremod FMLCorePlugin
   at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:260) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279) ~[launchwrapper-1.12.jar:?]
   at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176) ~[launchwrapper-1.12.jar:?]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_192]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_192]
   ... 35 more
Caused by: java.lang.RuntimeException: Attempted to load class net/minecraft/client/model/ModelCreeper for invalid side SERVER
   at net.minecraftforge.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:62) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:256) ~[forgeSrc-1.12.2-14.23.5.2768.jar:?]
   at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279) ~[launchwrapper-1.12.jar:?]
   at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176) ~[launchwrapper-1.12.jar:?]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_192]
   at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_192]
   ... 35 more