Program: 187512
Project: 187512
Buggy source:
private void sendDeathMessage(final EntityDeathEvent event){
  if (event.getEntity() instanceof CraftMyPet) {
    MyPet myPet=((CraftMyPet)event.getEntity()).getMyPet();
    String killer;
    if (event.getEntity().getLastDamageCause() instanceof EntityDamageByEntityEvent) {
      EntityDamageByEntityEvent e=(EntityDamageByEntityEvent)event.getEntity().getLastDamageCause();
      if (e.getDamager().getType() == EntityType.PLAYER) {
        if (e.getDamager() == myPet.getOwner().getPlayer()) {
          killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
        }
 else {
          killer=((Player)e.getDamager()).getName();
        }
      }
 else       if (e.getDamager().getType() == EntityType.WOLF) {
        Wolf w=(Wolf)e.getDamager();
        killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
        if (w.isTamed()) {
          killer+="String_Node_Str" + w.getOwner().getName() + ')';
        }
      }
 else       if (e.getDamager() instanceof CraftMyPet) {
        CraftMyPet craftMyPet=(CraftMyPet)e.getDamager();
        killer=craftMyPet.getMyPet().getPetName() + "String_Node_Str" + craftMyPet.getOwner().getName()+ ')';
      }
 else       if (e.getDamager() instanceof Projectile) {
        Projectile projectile=(Projectile)e.getDamager();
        killer=Locales.getString("String_Node_Str" + Util.capitalizeName(projectile.getType().name()),myPet.getOwner().getLanguage()) + "String_Node_Str";
        if (projectile.getShooter() instanceof Player) {
          if (projectile.getShooter() == myPet.getOwner().getPlayer()) {
            killer+=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
          }
 else {
            killer+=((Player)projectile.getShooter()).getName();
          }
        }
 else {
          if (MyPetType.isLeashableEntityType(e.getDamager().getType())) {
            killer=Locales.getString("String_Node_Str" + Util.capitalizeName(MyPetType.getMyPetTypeByEntityType(e.getDamager().getType()).getTypeName()),myPet.getOwner().getLanguage());
          }
 else {
            killer=Locales.getString("String_Node_Str" + Util.capitalizeName(e.getDamager().getType().getName()),myPet.getOwner().getLanguage());
          }
        }
        killer+="String_Node_Str";
      }
 else {
        if (MyPetType.isLeashableEntityType(e.getDamager().getType())) {
          killer=Locales.getString("String_Node_Str" + Util.capitalizeName(MyPetType.getMyPetTypeByEntityType(e.getDamager().getType()).getTypeName()),myPet.getOwner().getLanguage());
        }
 else {
          killer=Locales.getString("String_Node_Str" + Util.capitalizeName(e.getDamager().getType().getName()),myPet.getOwner().getLanguage());
        }
      }
    }
 else {
      if (event.getEntity().getLastDamageCause() != null) {
        killer=Locales.getString("String_Node_Str" + Util.capitalizeName(event.getEntity().getLastDamageCause().getCause().name()),myPet.getOwner().getLanguage());
      }
 else {
        killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
      }
    }
    myPet.sendMessageToOwner(Util.formatText(Locales.getString("String_Node_Str",myPet.getOwner().getLanguage()),myPet.getPetName(),killer));
  }
}

Fixed version (ground truth):
private void sendDeathMessage(final EntityDeathEvent event){
  if (event.getEntity() instanceof CraftMyPet) {
    MyPet myPet=((CraftMyPet)event.getEntity()).getMyPet();
    String killer;
    if (event.getEntity().getLastDamageCause() instanceof EntityDamageByEntityEvent) {
      EntityDamageByEntityEvent e=(EntityDamageByEntityEvent)event.getEntity().getLastDamageCause();
      if (e.getDamager().getType() == EntityType.PLAYER) {
        if (e.getDamager() == myPet.getOwner().getPlayer()) {
          killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
        }
 else {
          killer=((Player)e.getDamager()).getName();
        }
      }
 else       if (e.getDamager().getType() == EntityType.WOLF) {
        Wolf w=(Wolf)e.getDamager();
        killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
        if (w.isTamed()) {
          killer+="String_Node_Str" + w.getOwner().getName() + ')';
        }
      }
 else       if (e.getDamager() instanceof CraftMyPet) {
        CraftMyPet craftMyPet=(CraftMyPet)e.getDamager();
        killer=craftMyPet.getMyPet().getPetName() + "String_Node_Str" + craftMyPet.getOwner().getName()+ ')';
      }
 else       if (e.getDamager() instanceof Projectile) {
        Projectile projectile=(Projectile)e.getDamager();
        killer=Locales.getString("String_Node_Str" + Util.capitalizeName(projectile.getType().name()),myPet.getOwner().getLanguage()) + "String_Node_Str";
        if (projectile.getShooter() instanceof Player) {
          if (projectile.getShooter() == myPet.getOwner().getPlayer()) {
            killer+=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
          }
 else {
            killer+=((Player)projectile.getShooter()).getName();
          }
        }
 else {
          if (MyPetType.isLeashableEntityType(e.getDamager().getType())) {
            killer=Locales.getString("String_Node_Str" + Util.capitalizeName(MyPetType.getMyPetTypeByEntityType(e.getDamager().getType()).getTypeName()),myPet.getOwner().getLanguage());
          }
 else           if (e.getDamager().getType().getName() != null) {
            killer=Locales.getString("String_Node_Str" + Util.capitalizeName(e.getDamager().getType().getName()),myPet.getOwner().getLanguage());
          }
 else {
            killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
          }
        }
        killer+="String_Node_Str";
      }
 else {
        if (MyPetType.isLeashableEntityType(e.getDamager().getType())) {
          killer=Locales.getString("String_Node_Str" + Util.capitalizeName(MyPetType.getMyPetTypeByEntityType(e.getDamager().getType()).getTypeName()),myPet.getOwner().getLanguage());
        }
 else {
          killer=Locales.getString("String_Node_Str" + Util.capitalizeName(e.getDamager().getType().getName()),myPet.getOwner().getLanguage());
        }
      }
    }
 else {
      if (event.getEntity().getLastDamageCause() != null) {
        killer=Locales.getString("String_Node_Str" + Util.capitalizeName(event.getEntity().getLastDamageCause().getCause().name()),myPet.getOwner().getLanguage());
      }
 else {
        killer=Locales.getString("String_Node_Str",myPet.getOwner().getLanguage());
      }
    }
    myPet.sendMessageToOwner(Util.formatText(Locales.getString("String_Node_Str",myPet.getOwner().getLanguage()),myPet.getPetName(),killer));
  }
}