Fix build

src/main/java/com/minelittlepony/unicopia/entity/Living.java

@@ -483,8 +483,8 @@ public abstract class Living<T extends LivingEntity> implements Equine<T>, Caste
 
     public Optional<Boolean> onDamage(DamageSource source, float amount) {
 
-        if ((source.getAttacker() instanceof Guest guest && guest.getHost() instanceof Living l && l == this)
+        if (Guest.of(source.getAttacker()).hostIs(this)
-            || (source.getSource() instanceof Guest guest && guest.getHost() instanceof Living l && l == this)) {
+            || Guest.of(source.getSource()).hostIs(this)) {
             var type = source.getTypeRegistryEntry();
             return Optional.of(entity.damage(
                     type.matchesKey(DamageTypes.FIREBALL) ? entity.getDamageSources().create(DamageTypes.UNATTRIBUTED_FIREBALL) :
@@ -492,7 +492,7 @@ public abstract class Living<T extends LivingEntity> implements Equine<T>, Caste
                     new DamageSource(type, entity, entity), amount));
         }
 
-        if (entity instanceof Guest guest && guest.getHost() instanceof Living l) {
+        if (Guest.of(entity).getHost() instanceof Living l) {
             l.asEntity().damage(source, amount);
         }
 

src/main/java/com/minelittlepony/unicopia/entity/behaviour/Guest.java

@@ -1,15 +1,37 @@
 package com.minelittlepony.unicopia.entity.behaviour;
 
+import org.jetbrains.annotations.Nullable;
+
 import com.minelittlepony.unicopia.ability.magic.Caster;
 
 import net.minecraft.entity.Entity;
 
 public interface Guest {
-    void setHost(Caster<?> host);
+    Guest NULL = new Guest() {
+        @Override
+        public void setHost(@Nullable Caster<?> host) { }
 
+        @Nullable
+        @Override
+        public Caster<?> getHost() {
+            return null;
+        }
+    };
+
+    void setHost(@Nullable Caster<?> host);
+
+    @Nullable
     Caster<?> getHost();
 
-    static boolean hasHost(Entity entity) {
+    static Guest of(@Nullable Entity entity) {
-        return ((Guest)entity).getHost() != null;
+        return entity == null ? NULL : (Guest)entity;
+    }
+
+    default boolean hasHost() {
+        return getHost() != null;
+    }
+
+    default boolean hostIs(Caster<?> self) {
+        return getHost() == self;
     }
 }

src/main/java/com/minelittlepony/unicopia/entity/mob/CrystalShardsEntity.java

@@ -173,7 +173,7 @@ public class CrystalShardsEntity extends StationaryObjectEntity {
             }
         }
 
-        if (!Guest.hasHost(this)) {
+        if (!Guest.of(this).hasHost()) {
             if (isDead() || isInvalid(getWorld(), getBlockPos(), getAttachmentFace())) {
                 kill();
                 ParticleUtils.spawnParticles(ParticleTypes.CLOUD, this, 10);