Fix data watcher cloning in 1.16

Fixes #925

src/main/java/com/comphenix/protocol/wrappers/WrappedDataWatcher.java

@@ -35,6 +35,7 @@ import com.google.common.base.Optional;
 import com.google.common.collect.ImmutableBiMap;
 
 import org.apache.commons.lang.Validate;
+import org.bukkit.Bukkit;
 import org.bukkit.entity.Entity;
 import org.bukkit.inventory.ItemStack;
 
@@ -132,7 +133,8 @@ public class WrappedDataWatcher extends AbstractWrapper implements Iterable<Wrap
 					MinecraftReflection.getNmsWorldClass(), double.class, double.class, double.class);
 		}
 
-		return fakeEntity = eggConstructor.invoke(null, 0, 0, 0);
+		Object world = BukkitUnwrapper.getInstance().unwrapItem(Bukkit.getWorlds().get(0));
+		return fakeEntity = eggConstructor.invoke(world, 0, 0, 0);
 	}
 
 	// ---- Collection Methods
@@ -569,7 +571,12 @@ public class WrappedDataWatcher extends AbstractWrapper implements Iterable<Wrap
 			ENTITY_FIELD = Accessors.getFieldAccessor(HANDLE_TYPE, MinecraftReflection.getEntityClass(), true);
 		}
 
-		return (Entity) MinecraftReflection.getBukkitEntity(ENTITY_FIELD.get(handle));
+		Object entity = ENTITY_FIELD.get(handle);
+		if (entity == null) {
+			throw new NullPointerException(handle + "." + ENTITY_FIELD);
+		}
+
+		return (Entity) MinecraftReflection.getBukkitEntity(entity);
 	}
 
 	/**

src/test/java/com/comphenix/protocol/BukkitInitialization.java

@@ -1,17 +1,23 @@
 package com.comphenix.protocol;
 
+import java.util.Collections;
+import java.util.List;
+
+import com.comphenix.protocol.reflect.FieldUtils;
 import com.comphenix.protocol.utility.Constants;
-import com.comphenix.protocol.utility.MinecraftReflection;
-import com.comphenix.protocol.utility.MinecraftVersion;
 
 import net.minecraft.server.v1_16_R1.DispenserRegistry;
+import net.minecraft.server.v1_16_R1.WorldServer;
 
 import org.apache.logging.log4j.LogManager;
 import org.bukkit.Bukkit;
 import org.bukkit.Server;
+import org.bukkit.World;
 import org.bukkit.craftbukkit.v1_16_R1.CraftServer;
+import org.bukkit.craftbukkit.v1_16_R1.CraftWorld;
 import org.bukkit.craftbukkit.v1_16_R1.inventory.CraftItemFactory;
 import org.bukkit.craftbukkit.v1_16_R1.util.Versioning;
+import org.spigotmc.SpigotWorldConfig;
 
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
@@ -69,6 +75,22 @@ public class BukkitInitialization {
 			when(mockedServer.getItemFactory()).thenReturn(CraftItemFactory.instance());
 			when(mockedServer.isPrimaryThread()).thenReturn(true);
 
+			WorldServer nmsWorld = mock(WorldServer.class);
+
+			SpigotWorldConfig mockWorldConfig = mock(SpigotWorldConfig.class);
+
+			try {
+				FieldUtils.writeField(nmsWorld.getClass().getField("spigotConfig"), nmsWorld, mockWorldConfig, true);
+			} catch (ReflectiveOperationException ex) {
+				throw new RuntimeException(ex);
+			}
+
+			CraftWorld world = mock(CraftWorld.class);
+			when(world.getHandle()).thenReturn(nmsWorld);
+
+			List<World> worlds = Collections.singletonList(world);
+			when(mockedServer.getWorlds()).thenReturn(worlds);
+
 			// Inject this fake server
 			Bukkit.setServer(mockedServer);
 		}

src/test/java/com/comphenix/protocol/wrappers/WrappedDataWatcherTest.java

@@ -104,4 +104,14 @@ public class WrappedDataWatcherTest {
 		watcher.setObject(0, serializer, 1);
 		assertTrue(watcher.hasIndex(0));
 	}
+
+	@Test
+	public void testDeepClone() {
+		WrappedDataWatcher watcher = new WrappedDataWatcher();
+		watcher.setObject(0, Registry.get(Integer.class), 1);
+
+		WrappedDataWatcher cloned = watcher.deepClone();
+		assertEquals(1, cloned.asMap().size());
+		assertEquals(1, (Object) cloned.getInteger(0));
+	}
 }