Program: 12655
Project: 12655
Buggy source:
private static void init(FMLInitializationEvent event){
  Set<Biome> allBiomes=Biome.EXPLORATION_BIOMES_LIST;
  allBiomes.remove(Biomes.HELL);
  allBiomes.remove(Biomes.SKY);
  Set<Biome> zombieBiomes=Sets.newHashSet();
  zombieBiomes.addAll(allBiomes);
  Iterator<Biome> iterator=zombieBiomes.iterator();
  while (iterator.hasNext()) {
    Biome b=iterator.next();
    if (b != null) {
      if (!b.getBiomeClass().getName().startsWith("String_Node_Str") && !b.getBiomeClass().getName().startsWith("String_Node_Str")) {
        Iterator<Biome.SpawnListEntry> iterator2=b.getSpawnableList(EnumCreatureType.MONSTER).iterator();
        boolean zombie=false;
        while (iterator2.hasNext()) {
          if (iterator2.next().entityClass.equals(EntityZombie.class)) {
            zombie=true;
            break;
          }
        }
        if (!zombie) {
          VampirismMod.log.d("String_Node_Str","String_Node_Str",b);
          iterator.remove();
        }
      }
    }
  }
  registerEntity(EntityBlindingBat.class,BLINDING_BAT_NAME,EntityLiving.SpawnPlacementType.IN_AIR,false);
  registerEntity(EntityGhost.class,GHOST_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityConvertedCreature.class,CONVERTED_CREATURE,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityConvertedSheep.class,CONVERTED_SHEEP,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityBasicHunter.class,BASIC_HUNTER_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityBasicVampire.class,BASIC_VAMPIRE_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,Balance.mobProps.VAMPIRE_SPAWN_CHANCE,1,2,EnumCreatureType.MONSTER,zombieBiomes.toArray(new Biome[zombieBiomes.size()]));
  registerEntity(EntityHunterTrainer.class,HUNTER_TRAINER,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityAdvancedHunter.class,ADVANCED_HUNTER,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityVampireBaron.class,VAMPIRE_BARON,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityVampireMinionSaveable.class,VAMPIRE_MINION_SAVEABLE_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityDummyBittenAnimal.class,DUMMY_CREATURE,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityAdvancedVampire.class,ADVANCED_VAMPIRE,EntityLiving.SpawnPlacementType.ON_GROUND,Balance.mobProps.ADVANCED_VAMPIRE_SPAWN_PROBE,1,1,EnumCreatureType.MONSTER,zombieBiomes.toArray(new Biome[zombieBiomes.size()]));
  registerEntity(EntityConvertedVillager.class,CONVERTED_VILLAGER,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityHunterVillager.class,HUNTER_VILLAGER,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityCrossbowArrow.class,CROSSBOW_ARROW,EntityLiving.SpawnPlacementType.IN_AIR,false);
  registerConvertibles();
}

Fixed version (ground truth):
private static void init(FMLInitializationEvent event){
  Set<Biome> allBiomes=Biome.EXPLORATION_BIOMES_LIST;
  Set<Biome> zombieBiomes=Sets.newHashSet();
  zombieBiomes.addAll(allBiomes);
  zombieBiomes.remove(Biomes.MUSHROOM_ISLAND);
  zombieBiomes.remove(Biomes.MUSHROOM_ISLAND_SHORE);
  zombieBiomes.remove(Biomes.HELL);
  zombieBiomes.remove(Biomes.SKY);
  Iterator<Biome> iterator=zombieBiomes.iterator();
  while (iterator.hasNext()) {
    Biome b=iterator.next();
    if (b != null) {
      if (!b.getBiomeClass().getName().startsWith("String_Node_Str") && !b.getBiomeClass().getName().startsWith("String_Node_Str")) {
        Iterator<Biome.SpawnListEntry> iterator2=b.getSpawnableList(EnumCreatureType.MONSTER).iterator();
        boolean zombie=false;
        while (iterator2.hasNext()) {
          if (iterator2.next().entityClass.equals(EntityZombie.class)) {
            zombie=true;
            break;
          }
        }
        if (!zombie) {
          VampirismMod.log.d("String_Node_Str","String_Node_Str",b);
          iterator.remove();
        }
      }
    }
  }
  registerEntity(EntityBlindingBat.class,BLINDING_BAT_NAME,EntityLiving.SpawnPlacementType.IN_AIR,false);
  registerEntity(EntityGhost.class,GHOST_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityConvertedCreature.class,CONVERTED_CREATURE,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityConvertedSheep.class,CONVERTED_SHEEP,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityBasicHunter.class,BASIC_HUNTER_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityBasicVampire.class,BASIC_VAMPIRE_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,Balance.mobProps.VAMPIRE_SPAWN_CHANCE,1,2,EnumCreatureType.MONSTER,zombieBiomes.toArray(new Biome[zombieBiomes.size()]));
  registerEntity(EntityHunterTrainer.class,HUNTER_TRAINER,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityAdvancedHunter.class,ADVANCED_HUNTER,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityVampireBaron.class,VAMPIRE_BARON,EntityLiving.SpawnPlacementType.ON_GROUND,true);
  registerEntity(EntityVampireMinionSaveable.class,VAMPIRE_MINION_SAVEABLE_NAME,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityDummyBittenAnimal.class,DUMMY_CREATURE,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityAdvancedVampire.class,ADVANCED_VAMPIRE,EntityLiving.SpawnPlacementType.ON_GROUND,Balance.mobProps.ADVANCED_VAMPIRE_SPAWN_PROBE,1,1,EnumCreatureType.MONSTER,zombieBiomes.toArray(new Biome[zombieBiomes.size()]));
  registerEntity(EntityConvertedVillager.class,CONVERTED_VILLAGER,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityHunterVillager.class,HUNTER_VILLAGER,EntityLiving.SpawnPlacementType.ON_GROUND,false);
  registerEntity(EntityCrossbowArrow.class,CROSSBOW_ARROW,EntityLiving.SpawnPlacementType.IN_AIR,false);
  registerConvertibles();
}