Server stops every time I try to place a block

---- Minecraft Crash Report ----
// Surprise! Haha. Well, this is awkward.

Time: 4/15/20 11:56 PM
Description: Exception in server tick loop

java.lang.NoClassDefFoundError: net/minecraft/client/Minecraft
    at TMIConfig.isMultiplayer(TMIConfig.java:87)
    at TMIForgeContainer.playerInteract(TMIForgeContainer.java:48)
    at cpw.mods.fml.common.eventhandler.ASMEventHandler_1_TMIForgeContainer_playerInteract_PlayerInteractEvent.invoke(.dynamic)
    at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:54)
    at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:140)
    at net.minecraftforge.event.ForgeEventFactory.onPlayerInteract(ForgeEventFactory.java:100)
    at net.minecraft.server.management.ItemInWorldManager.func_73078_a(ItemInWorldManager.java:353)
    at net.minecraft.network.NetHandlerPlayServer.func_147346_a(NetHandlerPlayServer.java:556)
    at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:60)
    at net.minecraft.network.play.client.C08PacketPlayerBlockPlacement.func_148833_a(SourceFile:9)
    at net.minecraft.network.NetworkManager.func_74428_b(NetworkManager.java:212)
    at net.minecraft.network.NetworkSystem.func_151269_c(NetworkSystem.java:165)
    at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:659)
    at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:334)
    at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:547)
    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:427)
    at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:685)
Caused by: java.lang.ClassNotFoundException: net.minecraft.client.Minecraft
    at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:191)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    ... 17 more
Caused by: java.lang.RuntimeException: Attempted to load class bao for invalid side SERVER
    at cpw.mods.fml.common.asm.transformers.SideTransformer.transform(SideTransformer.java:50)
    at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
    at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
    ... 19 more

A detailed walkthrough of the error, its code path and all known details is as follows: