Program: 27609
Project: 27609
Buggy source:
@Overwrite protected void loadAllWorlds(String overworldFolder,String unused,long seed,WorldType type,String generator){
  this.convertMapIfNeeded(overworldFolder);
  this.setUserMessage("String_Node_Str");
  List<Integer> idList=new LinkedList<Integer>(Arrays.asList(DimensionManager.getStaticDimensionIDs()));
  idList.remove(Integer.valueOf(0));
  idList.add(0,0);
  for (  int dim : idList) {
    WorldProvider provider=WorldProvider.getProviderForDimension(dim);
    String worldFolder="String_Node_Str";
    if (dim == 0) {
      worldFolder=overworldFolder;
    }
 else {
      worldFolder=SpongeMod.instance.getSpongeRegistry().getWorldFolder(dim);
      if (worldFolder == null) {
        worldFolder=provider.getSaveFolder();
      }
    }
    WorldInfo worldInfo=null;
    WorldSettings newWorldSettings=null;
    AnvilSaveHandler worldsavehandler=null;
    worldsavehandler=new AnvilSaveHandler(new File(getFolderName()),worldFolder,true);
    worldInfo=worldsavehandler.loadWorldInfo();
    if (worldInfo == null) {
      newWorldSettings=new WorldSettings(seed,this.getGameType(),this.canStructuresSpawn(),this.isHardcore(),type);
      newWorldSettings.setWorldName(generator);
      if (this.enableBonusChest) {
        newWorldSettings.enableBonusChest();
      }
      worldInfo=new WorldInfo(newWorldSettings,worldFolder);
      ((IMixinWorldInfo)worldInfo).setUUID(UUID.randomUUID());
      if (dim == 0 || dim == -1 || dim == 1) {
        ((WorldProperties)worldInfo).setKeepSpawnLoaded(true);
        ((WorldProperties)worldInfo).setLoadOnStartup(true);
        ((WorldProperties)worldInfo).setEnabled(true);
        ((WorldProperties)worldInfo).setGeneratorType(GeneratorTypes.DEFAULT);
        SpongeMod.instance.getSpongeRegistry().registerWorldProperties((WorldProperties)worldInfo);
      }
    }
 else {
      worldInfo.setWorldName(worldFolder);
      newWorldSettings=new WorldSettings(worldInfo);
    }
    if (dim == 0) {
      this.setResourcePackFromWorld(this.getFolderName(),worldsavehandler);
    }
    ((IMixinWorldInfo)worldInfo).setDimensionId(dim);
    ((IMixinWorldInfo)worldInfo).setDimensionType(((Dimension)provider).getType());
    UUID uuid=((WorldProperties)worldInfo).getUniqueId();
    SpongeMod.instance.getSpongeRegistry().registerWorldUniqueId(uuid,worldFolder);
    WorldServer world=(WorldServer)new WorldServer((MinecraftServer)(Object)this,worldsavehandler,worldInfo,dim,this.theProfiler).init();
    world.initialize(newWorldSettings);
    world.addWorldAccess(new WorldManager((MinecraftServer)(Object)this,world));
    if (!this.isSinglePlayer()) {
      world.getWorldInfo().setGameType(this.getGameType());
    }
    SpongeMod.instance.getSpongeRegistry().registerWorldProperties((WorldProperties)worldInfo);
    net.minecraftforge.common.MinecraftForge.EVENT_BUS.post(new net.minecraftforge.event.world.WorldEvent.Load(world));
  }
  this.serverConfigManager.setPlayerManager(new WorldServer[]{DimensionManager.getWorld(0)});
  this.setDifficultyForAllWorlds(this.getDifficulty());
  this.initialWorldChunkLoad();
}

Fixed version (ground truth):
@Overwrite protected void loadAllWorlds(String overworldFolder,String unused,long seed,WorldType type,String generator){
  this.convertMapIfNeeded(overworldFolder);
  this.setUserMessage("String_Node_Str");
  List<Integer> idList=new LinkedList<Integer>(Arrays.asList(DimensionManager.getStaticDimensionIDs()));
  idList.remove(Integer.valueOf(0));
  idList.add(0,0);
  for (  int dim : idList) {
    WorldProvider provider=WorldProvider.getProviderForDimension(dim);
    String worldFolder="String_Node_Str";
    if (dim == 0) {
      worldFolder=overworldFolder;
    }
 else {
      worldFolder=SpongeMod.instance.getSpongeRegistry().getWorldFolder(dim);
      if (worldFolder != null) {
        final Optional<World> optExisting=getWorld(worldFolder);
        if (optExisting.isPresent()) {
          continue;
        }
      }
 else {
        worldFolder=provider.getSaveFolder();
      }
    }
    WorldInfo worldInfo=null;
    WorldSettings newWorldSettings=null;
    AnvilSaveHandler worldsavehandler=null;
    if (FMLCommonHandler.instance().getSide() == Side.CLIENT) {
      worldsavehandler=new AnvilSaveHandler(new File(dim == 0 ? "String_Node_Str" : FMLCommonHandler.instance().getSavesDirectory() + File.separator + getFolderName()),worldFolder,true);
    }
 else {
      worldsavehandler=new AnvilSaveHandler(new File(dim == 0 ? "String_Node_Str" : getFolderName()),worldFolder,true);
    }
    worldInfo=worldsavehandler.loadWorldInfo();
    if (worldInfo == null) {
      newWorldSettings=new WorldSettings(seed,this.getGameType(),this.canStructuresSpawn(),this.isHardcore(),type);
      newWorldSettings.setWorldName(generator);
      if (this.enableBonusChest) {
        newWorldSettings.enableBonusChest();
      }
      worldInfo=new WorldInfo(newWorldSettings,worldFolder);
      ((IMixinWorldInfo)worldInfo).setUUID(UUID.randomUUID());
      if (dim == 0 || dim == -1 || dim == 1) {
        ((WorldProperties)worldInfo).setKeepSpawnLoaded(true);
        ((WorldProperties)worldInfo).setLoadOnStartup(true);
        ((WorldProperties)worldInfo).setEnabled(true);
        ((WorldProperties)worldInfo).setGeneratorType(GeneratorTypes.DEFAULT);
        SpongeMod.instance.getSpongeRegistry().registerWorldProperties((WorldProperties)worldInfo);
      }
    }
 else {
      worldInfo.setWorldName(worldFolder);
      newWorldSettings=new WorldSettings(worldInfo);
    }
    if (dim == 0) {
      this.setResourcePackFromWorld(this.getFolderName(),worldsavehandler);
    }
    ((IMixinWorldInfo)worldInfo).setDimensionId(dim);
    ((IMixinWorldInfo)worldInfo).setDimensionType(((Dimension)provider).getType());
    UUID uuid=((WorldProperties)worldInfo).getUniqueId();
    SpongeMod.instance.getSpongeRegistry().registerWorldUniqueId(uuid,worldFolder);
    WorldServer world=(WorldServer)new WorldServer((MinecraftServer)(Object)this,worldsavehandler,worldInfo,dim,this.theProfiler).init();
    world.initialize(newWorldSettings);
    world.addWorldAccess(new WorldManager((MinecraftServer)(Object)this,world));
    if (!this.isSinglePlayer()) {
      world.getWorldInfo().setGameType(this.getGameType());
    }
    SpongeMod.instance.getSpongeRegistry().registerWorldProperties((WorldProperties)worldInfo);
    net.minecraftforge.common.MinecraftForge.EVENT_BUS.post(new net.minecraftforge.event.world.WorldEvent.Load(world));
  }
  this.serverConfigManager.setPlayerManager(new WorldServer[]{DimensionManager.getWorld(0)});
  this.setDifficultyForAllWorlds(this.getDifficulty());
  this.initialWorldChunkLoad();
}