Fix World Capabilities NPE when there are no attached capabilities.

src/main/java/net/minecraftforge/common/util/WorldCapabilityData.java

@@ -26,7 +26,7 @@ public class WorldCapabilityData extends WorldSavedData
     public void readFromNBT(NBTTagCompound nbt)
     {
         this.capNBT = nbt;
-        if(serializable != null)
+        if (serializable != null)
         {
             serializable.deserializeNBT(this.capNBT);
             this.capNBT = null;
@@ -36,7 +36,9 @@ public class WorldCapabilityData extends WorldSavedData
     @Override
     public NBTTagCompound writeToNBT(NBTTagCompound nbt)
     {
-        return nbt = serializable.serializeNBT();
+        if (serializable != null)
+            nbt = serializable.serializeNBT();
+        return nbt;
     }
 
     @Override
@@ -48,7 +50,7 @@ public class WorldCapabilityData extends WorldSavedData
     public void setCapabilities(WorldProvider provider, INBTSerializable<NBTTagCompound> capabilities)
     {
         this.serializable = capabilities;
-        if(this.capNBT != null)
+        if (this.capNBT != null)
         {
             serializable.deserializeNBT(this.capNBT);
             this.capNBT = null;

src/main/java/net/minecraftforge/event/ForgeEventFactory.java

@@ -489,7 +489,7 @@ public class ForgeEventFactory
     {
         MinecraftForge.EVENT_BUS.post(new PotionBrewEvent.Post(brewingItemStacks));
     }
-    
+
     public static void onPlayerBrewedPotion(EntityPlayer player, ItemStack stack)
     {
         MinecraftForge.EVENT_BUS.post(new PlayerBrewedPotionEvent(player, stack));
@@ -525,7 +525,8 @@ public class ForgeEventFactory
         return gatherCapabilities(new AttachCapabilitiesEvent.Item(item, stack), parent);
     }
 
-    public static CapabilityDispatcher gatherCapabilities(World world, ICapabilityProvider parent) {
+    public static CapabilityDispatcher gatherCapabilities(World world, ICapabilityProvider parent)
+    {
         return gatherCapabilities(new AttachCapabilitiesEvent.World(world), parent);
     }