Fix crash x3

build.gradle.kts

@@ -40,6 +40,8 @@ dependencies {
     modImplementation("dev.ithundxr.createnumismatics:CreateNumismatics-fabric-1.20.1:1.0.6+fabric-mc1.20.1")
 
     modCompileOnly("maven.modrinth:copycats:fabric.1.20.1-1.3.2")
+
+    modCompileOnly("maven.modrinth:appleskin:2.5.1+mc1.20")
 }
 
 tasks.processResources {

src/main/java/dev/ithundxr/railwaystweaks/mixin/compat/appleskin/SyncHandlerMixin.java

@@ -0,0 +1,19 @@
+package dev.ithundxr.railwaystweaks.mixin.compat.appleskin;
+
+import net.minecraft.server.level.ServerPlayer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Pseudo;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import squeek.appleskin.network.SyncHandler;
+
+@Pseudo
+@Mixin(SyncHandler.class)
+public class SyncHandlerMixin {
+    @Inject(method = "onPlayerUpdate", at = @At("HEAD"), cancellable = true)
+    private static void railwaysTweaks$fixAppleSkinCrash(ServerPlayer player, CallbackInfo ci) {
+        if (player.connection == null)
+            ci.cancel();
+    }
+}

src/main/resources/railwaystweaks.mixins.json

@@ -4,9 +4,10 @@
   "package": "dev.ithundxr.railwaystweaks.mixin",
   "compatibilityLevel": "JAVA_17",
   "mixins": [
-    "ServerPlayerMixin",
     "LivingEntityMixin",
-    "ServerStatusPacketListenerImplMixin"
+    "ServerPlayerMixin",
+    "ServerStatusPacketListenerImplMixin",
+    "compat.appleskin.SyncHandlerMixin"
   ],
   "client": [
     "client.HttpTextureMixin",