Fix plugin not loading properly if spawner is removed while the plugin was disabled

UltimateStacker-Plugin/src/main/java/com.craftaro.ultimatestacker/stackable/spawner/SpawnerStackImpl.java

@@ -159,6 +159,9 @@ public class SpawnerStackImpl implements SpawnerStack {
             return null;
         }
         CreatureSpawner creatureSpawner = (CreatureSpawner) this.location.getBlock().getState();
+        if (creatureSpawner.getSpawnedType() == null) {
+            return null;
+        }
         return Methods.compileSpawnerName(creatureSpawner.getSpawnedType(), this.amount);
     }