fix: multiplayer crash

build.gradle

@@ -24,7 +24,7 @@ apply from: './gradle/scripts/mixins.gradle'
 sourceCompatibility = JavaVersion.VERSION_1_8
 targetCompatibility = JavaVersion.VERSION_1_8
 
-version = "1.7.0"
+version = "1.7.1"
 group= "dev.tilera.modding"
 archivesBaseName = "cwg"
 

src/main/java/dev/tilera/cwg/ClassicWorldgen.java

@@ -1,6 +1,7 @@
 package dev.tilera.cwg;
 
 import cpw.mods.fml.common.Mod;
+import cpw.mods.fml.common.SidedProxy;
 import cpw.mods.fml.common.Mod.EventHandler;
 import cpw.mods.fml.common.event.FMLInitializationEvent;
 import cpw.mods.fml.common.event.FMLPreInitializationEvent;
@@ -9,7 +10,7 @@ import cpw.mods.fml.common.eventhandler.SubscribeEvent;
 import dev.tilera.cwg.caves.MapGenCavesSwiss;
 import dev.tilera.cwg.command.CommandChangeWorld;
 import dev.tilera.cwg.noisegen.NoiseGeneratorOctavesFarlands;
-import net.minecraft.server.MinecraftServer;
+import dev.tilera.cwg.proxy.CommonProxy;
 import net.minecraft.world.World;
 import net.minecraft.world.WorldType;
 import net.minecraft.world.biome.BiomeGenBase;
@@ -27,6 +28,8 @@ public class ClassicWorldgen {
 
     @Mod.Instance
     public static ClassicWorldgen INSTANCE;
+    @SidedProxy(modId = Constants.ID, serverSide = "dev.tilera.cwg.proxy.CommonProxy", clientSide = "dev.tilera.cwg.proxy.ClientProxy")
+    public static CommonProxy proxy;
 
     @EventHandler
     public void preInit(FMLPreInitializationEvent event) {
@@ -70,9 +73,7 @@ public class ClassicWorldgen {
     }
 
     public static boolean isClassicWorld() {
-        World[] worlds = MinecraftServer.getServer().worldServers;
-        if (worlds.length == 0) return true;
-        World world = worlds[0];
+        World world = proxy.getWorld();
         if (world == null) return true;
         return isClassicWorld(world);
     }

src/main/java/dev/tilera/cwg/proxy/ClientProxy.java

@@ -0,0 +1,22 @@
+package dev.tilera.cwg.proxy;
+
+import net.minecraft.client.Minecraft;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.World;
+
+public class ClientProxy extends CommonProxy {
+
+    @Override
+    public World getWorld() {
+        World world = null;
+        if (MinecraftServer.getServer() != null) {
+            World[] worlds = MinecraftServer.getServer().worldServers;
+            if (worlds.length == 0) return null;
+            world = worlds[0];
+        } else if (Minecraft.getMinecraft() != null) {
+            world = Minecraft.getMinecraft().theWorld;
+        }
+        return world;
+    }
+
+}

src/main/java/dev/tilera/cwg/proxy/CommonProxy.java

@@ -0,0 +1,14 @@
+package dev.tilera.cwg.proxy;
+
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.World;
+
+public class CommonProxy {
+    
+    public World getWorld() {
+        World[] worlds = MinecraftServer.getServer().worldServers;
+        if (worlds.length == 0) return null;
+        return worlds[0];
+    }
+
+}