fix(world): skip prefab components with no registered metadata instead of NPEing

ComponentLibrary.copy() returns null for a component class with no
registered metadata (e.g. an optional-dependency module not loaded); these
three call sites passed that straight into addComponent() -> NPE.
BlockPrefabManager.updateBlock() already guards this; applied the same
skip-and-log pattern here. Found via a live crash: ManualLabor:ShapingTable
referencing MachineDefinitionComponent with `machines` not loaded.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: soloturn

engine/src/main/java/org/terasology/engine/world/block/items/BlockItemFactory.java

@@ -4,6 +4,8 @@
 
 import com.google.common.base.Preconditions;
 import com.google.common.primitives.SignedBytes;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.terasology.engine.entitySystem.ComponentContainer;
 import org.terasology.engine.entitySystem.entity.EntityBuilder;
 import org.terasology.engine.entitySystem.entity.EntityManager;
@@ -37,6 +39,8 @@
  * @see RetainComponentsComponent
  */
 public class BlockItemFactory {
+    private static final Logger logger = LoggerFactory.getLogger(BlockItemFactory.class);
+
     private final EntityManager entityManager;
 
     /**
@@ -186,7 +190,14 @@ private void addComponents(EntityBuilder builder, ComponentContainer components)
 
         for (Component component : components.iterateComponents()) {
             if (keepByAnnotation(component) || retainComponents.contains(component.getClass())) {
-                builder.addComponent(entityManager.getComponentLibrary().copy(component));
+                Component copy = entityManager.getComponentLibrary().copy(component);
+                if (copy == null) {
+                    // No registered ComponentMetadata for component's class, most likely because a
+                    // module it depends on isn't loaded - see BlockPrefabManager.updateBlock().
+                    logger.error("No ComponentMetadata for {} - skipping", component.getClass().getName());
+                    continue;
+                }
+                builder.addComponent(copy);
             }
         }
     }

engine/src/main/java/org/terasology/engine/world/block/typeEntity/BlockTypeEntityGenerator.java

@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: Apache-2.0
 package org.terasology.engine.world.block.typeEntity;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.terasology.engine.entitySystem.entity.EntityBuilder;
 import org.terasology.engine.entitySystem.entity.EntityManager;
 import org.terasology.engine.entitySystem.entity.EntityRef;
@@ -18,6 +20,8 @@
 
 public class BlockTypeEntityGenerator implements BlockRegistrationListener {
 
+    private static final Logger logger = LoggerFactory.getLogger(BlockTypeEntityGenerator.class);
+
     private EntityManager entityManager;
     private PrefabManager prefabManager;
     private BlockManager blockManager;
@@ -69,7 +73,17 @@ private void generateBlockTypeEntity(Block block) {
         if (prefab.isPresent()) {
             for (Component comp : prefab.get().iterateComponents()) {
                 if (!(comp instanceof NetworkComponent)) {
-                    builder.addComponent(entityManager.getComponentLibrary().copy(comp));
+                    Component copy = entityManager.getComponentLibrary().copy(comp);
+                    if (copy == null) {
+                        // No registered ComponentMetadata for comp's class, most likely because a
+                        // module it depends on isn't loaded - see the matching guard and explanation
+                        // in BlockPrefabManager.updateBlock(). Skip it rather than NPE and take the
+                        // whole block type entity down.
+                        logger.error("No ComponentMetadata for {}, referenced by block {}'s prefab {} - skipping",
+                                comp.getClass().getName(), block.getURI(), prefab.get().getUrn());
+                        continue;
+                    }
+                    builder.addComponent(copy);
                 }
             }
         }

engine/src/main/java/org/terasology/engine/world/internal/EntityAwareWorldProvider.java

@@ -474,7 +474,15 @@ private void cleanUpTemporaryEntity(EntityRef entity) {
             for (Component comp : prefab.iterateComponents()) {
                 Component currentComp = entity.getComponent(comp.getClass());
                 if (currentComp == null) {
-                    entity.addComponent(entityManager.getComponentLibrary().copy(comp));
+                    Component copy = entityManager.getComponentLibrary().copy(comp);
+                    if (copy == null) {
+                        // No registered ComponentMetadata for comp's class, most likely because a
+                        // module it depends on isn't loaded - see BlockPrefabManager.updateBlock().
+                        logger.error("No ComponentMetadata for {}, referenced by prefab {} - skipping",
+                                comp.getClass().getName(), prefab.getUrn());
+                        continue;
+                    }
+                    entity.addComponent(copy);
                 } else {
                     ComponentMetadata<?> metadata = entityManager.getComponentLibrary().getMetadata(comp.getClass());
                     boolean changed = false;