Fixed NotSerializableException when sacrificing entities (fixes #666)

Author: Intelli

src/main/java/net/coreprotect/listener/entity/EntityDeathListener.java

@@ -289,7 +289,7 @@ else if (entity instanceof Player) {
                     if (attributeInstance != null) {
                         List<Object> attributeData = new ArrayList<>();
                         List<Object> attributeModifiers = new ArrayList<>();
-                        attributeData.add(attributeInstance.getAttribute());
+                        attributeData.add(BukkitAdapter.ADAPTER.getRegistryKey(attributeInstance.getAttribute()));
                         attributeData.add(attributeInstance.getBaseValue());
 
                         for (AttributeModifier modifier : attributeInstance.getModifiers()) {

src/main/java/net/coreprotect/utility/entity/EntityUtil.java

@@ -166,7 +166,13 @@ else if (count == 1) {
                     for (Object value : attributes) {
                         @SuppressWarnings("unchecked")
                         List<Object> attributeData = (List<Object>) value;
-                        Attribute attribute = (Attribute) attributeData.get(0);
+                        Attribute attribute = null;
+                        if (attributeData.get(0) instanceof Attribute) {
+                            attribute = (Attribute) attributeData.get(0);
+                        }
+                        else {
+                            attribute = (Attribute) BukkitAdapter.ADAPTER.getRegistryValue((String) attributeData.get(0), Attribute.class);
+                        }
                         Double baseValue = (Double) attributeData.get(1);
                         @SuppressWarnings("unchecked")
                         List<Object> attributeModifiers = (List<Object>) attributeData.get(2);