Fixed crash due to null interpolator id, and fixed crash when entities other than the player hold an item

src/main/java/com/minelittlepony/client/mixin/MixinFirstPersonRenderer.java

@@ -8,7 +8,6 @@ import com.minelittlepony.client.render.PonyRenderDispatcher;
 
 import javax.annotation.Nullable;
 
-import net.minecraft.client.network.AbstractClientPlayerEntity;
 import net.minecraft.client.render.FirstPersonRenderer;
 import net.minecraft.client.render.VertexConsumerProvider;
 import net.minecraft.client.render.model.json.ModelTransformation.Type;
@@ -43,6 +42,6 @@ abstract class MixinFirstPersonRenderer {
             VertexConsumerProvider renderContext,
             @Nullable World world,
             int lightUv, int overlayUv) {
-        PonyRenderDispatcher.getInstance().getMagicRenderer().renderItemInFirstPerson(target, (AbstractClientPlayerEntity)entity, item, transform, left, stack, renderContext, world, lightUv);
+        PonyRenderDispatcher.getInstance().getMagicRenderer().renderItemInFirstPerson(target, entity, item, transform, left, stack, renderContext, world, lightUv);
     }
 }

src/main/java/com/minelittlepony/client/model/ClientPonyModel.java

@@ -30,7 +30,7 @@ public abstract class ClientPonyModel<T extends LivingEntity> extends MsonPlayer
     /**
      * Associated pony data.
      */
-    protected IPonyData metadata = new PonyData();
+    protected IPonyData metadata = PonyData.NULL;
 
     @Override
     public void updateLivingState(T entity, IPony pony, EquineRenderManager.Mode mode) {

src/main/java/com/minelittlepony/client/model/PonySkullModel.java

@@ -23,7 +23,7 @@ public class PonySkullModel extends SkullOverlayEntityModel implements MsonModel
 
     private ModelPart hair;
 
-    public IPonyData metadata = new PonyData();
+    public IPonyData metadata = PonyData.NULL;
 
     @Override
     public void init(ModelContext context) {

src/main/java/com/minelittlepony/client/pony/PonyData.java

@@ -35,13 +35,15 @@ public class PonyData implements IPonyData {
 
     private static final PonyDataSerialiser SERIALISER = new PonyDataSerialiser();
 
+    public static final IPonyData NULL = new PonyData(Race.HUMAN);
+
     /**
      * Parses the given resource into a new IPonyData.
      * This may either come from an attached json file or the image itself.
      */
     public static IPonyData parse(@Nullable Identifier identifier) {
         if (identifier == null) {
-            return new PonyData();
+            return NULL;
         }
 
         try (Resource res = MinecraftClient.getInstance().getResourceManager().getResource(identifier)) {
@@ -60,7 +62,7 @@ public class PonyData implements IPonyData {
             return NativeUtil.parseImage(identifier, PonyData::new);
         } catch (IllegalStateException e) {
             MineLittlePony.logger.fatal("Unable to read {} metadata", identifier, e);
-            return new PonyData();
+            return NULL;
         }
     }
 
@@ -82,8 +84,8 @@ public class PonyData implements IPonyData {
     @Expose
     private final boolean[] wearables;
 
-    public PonyData() {
-        race = Race.HUMAN;
+    public PonyData(Race race) {
+        this.race = race;
         tailSize = TailLength.FULL;
         gender = Gender.MARE;
         size = Size.NORMAL;

src/main/java/com/minelittlepony/client/pony/PonyManager.java

@@ -70,7 +70,7 @@ public class PonyManager implements IPonyManager, IdentifiableResourceReloadList
         try {
             return poniesCache.get(resource);
         } catch (ExecutionException e) {
-            return new Pony(resource, new PonyData());
+            return new Pony(resource, PonyData.NULL);
         }
     }
 

src/main/java/com/minelittlepony/client/render/LevitatingItemRenderer.java

@@ -7,7 +7,6 @@ import com.minelittlepony.util.Color;
 import javax.annotation.Nullable;
 
 import net.minecraft.client.MinecraftClient;
-import net.minecraft.client.network.AbstractClientPlayerEntity;
 import net.minecraft.client.render.OverlayTexture;
 import net.minecraft.client.render.RenderLayer;
 import net.minecraft.client.render.VertexConsumerProvider;
@@ -17,6 +16,7 @@ import net.minecraft.client.texture.SpriteAtlasTexture;
 import net.minecraft.client.util.math.MatrixStack;
 import net.minecraft.client.util.math.Vector3f;
 import net.minecraft.entity.LivingEntity;
+import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.item.ItemStack;
 import net.minecraft.util.Arm;
 import net.minecraft.util.Identifier;
@@ -76,8 +76,11 @@ public class LevitatingItemRenderer {
     /**
      * Renders an item in first person optionally with a magical overlay.
      */
-    public void renderItemInFirstPerson(ItemRenderer itemRenderer, @Nullable AbstractClientPlayerEntity entity, ItemStack stack, ModelTransformation.Type transform, boolean left, MatrixStack matrix, VertexConsumerProvider renderContext, @Nullable World world, int lightUv) {
-        IPony pony = MineLittlePony.getInstance().getManager().getPony(entity);
+    public void renderItemInFirstPerson(ItemRenderer itemRenderer, @Nullable LivingEntity entity, ItemStack stack, ModelTransformation.Type transform, boolean left, MatrixStack matrix, VertexConsumerProvider renderContext, @Nullable World world, int lightUv) {
+
+        if (entity instanceof PlayerEntity) {
+
+            IPony pony = MineLittlePony.getInstance().getManager().getPony((PlayerEntity)entity);
 
             matrix.push();
 
@@ -103,6 +106,9 @@ public class LevitatingItemRenderer {
             }
 
             matrix.pop();
+        } else {
+            itemRenderer.method_23177(entity, stack, transform, left, matrix, renderContext, world, lightUv, OverlayTexture.DEFAULT_UV);
+        }
     }
 
     /**

src/main/java/com/minelittlepony/model/ModelAttributes.java

@@ -70,7 +70,7 @@ public class ModelAttributes<T extends LivingEntity> {
      * Unique id of the interpolator used for this model.
      * Usually the UUID of the entity being rendered.
      */
-    public UUID interpolatorId;
+    public UUID interpolatorId = UUID.randomUUID();
 
     /**
      * The actual, visible height of this model when rendered.