Program: 86618
Project: 86618
Buggy source:
private void player(Player player,String[] args){
  if (args.length == 2) {
    LineTracer tracer=new LineTracer(player);
    Block b=tracer.getTargetBlock();
    if (b != null) {
      b.setY(b.getY() + 1);
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        if (mob.spawn()) {
          player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1]));
        }
 else {
          player.notice("String_Node_Str");
        }
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
 else {
      player.notice("String_Node_Str");
    }
  }
  if (args.length == 3) {
    if (args[2].matches("String_Node_Str")) {
      int amount=Integer.parseInt(args[2]);
      LineTracer tracer=new LineTracer(player);
      Block b=tracer.getTargetBlock();
      if (b == null) {
        player.notice("String_Node_Str");
        return;
      }
      b.setY(b.getY() + 1);
      boolean spawnSuccess=true;
      for (int i=0; i < amount; ++i) {
        try {
          Entity e=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
          e.spawn();
        }
 catch (        IllegalArgumentException e) {
          player.notice("String_Node_Str");
        }
      }
      if (spawnSuccess) {
        player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1]));
      }
 else {
        player.notice(Translator.translate("String_Node_Str"));
      }
    }
 else {
      LineTracer tracer=new LineTracer(player);
      Block b=tracer.getTargetBlock();
      if (b == null) {
        player.notice("String_Node_Str");
        return;
      }
      b.setY(b.getY() + 1);
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        Entity rider=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[2].toUpperCase()));
        mob.spawn(rider);
        player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1],args[2]));
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
  }
  if (args.length == 4) {
    if (!args[3].matches("String_Node_Str")) {
      player.notice(Translator.translate("String_Node_Str"));
      Canary.help().getHelp(player,"String_Node_Str");
      return;
    }
    int amount=Integer.parseInt(args[3]);
    LineTracer tracer=new LineTracer(player);
    Block b=tracer.getTargetBlock();
    if (b == null) {
      player.notice("String_Node_Str");
      return;
    }
    b.setY(b.getY() + 1);
    boolean spawnSuccess=true;
    for (int i=0; i < amount; ++i) {
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        Entity rider=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[2].toUpperCase()));
        mob.spawn(rider);
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
    if (spawnSuccess) {
      player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1],args[2]));
    }
 else {
      player.notice(Translator.translate("String_Node_Str"));
    }
  }
}

Fixed version (ground truth):
private void player(Player player,String[] args){
  if (args.length == 2) {
    LineTracer tracer=new LineTracer(player);
    Block b=tracer.getTargetBlock();
    if (b != null) {
      b.setY(b.getY() + 1);
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        if (mob.spawn()) {
          player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1]));
        }
 else {
          player.notice("String_Node_Str");
        }
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
 else {
      player.notice("String_Node_Str");
    }
  }
  if (args.length == 3) {
    if (args[2].matches("String_Node_Str")) {
      int amount=Integer.parseInt(args[2]);
      LineTracer tracer=new LineTracer(player);
      Block b=tracer.getTargetBlock();
      if (b == null) {
        player.notice("String_Node_Str");
        return;
      }
      b.setY(b.getY() + 1);
      boolean spawnSuccess=true;
      for (int i=0; i < amount; ++i) {
        try {
          Entity e=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
          spawnSuccess&=e.spawn();
        }
 catch (        IllegalArgumentException e) {
          player.notice("String_Node_Str");
        }
      }
      if (spawnSuccess) {
        player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1]));
      }
 else {
        player.notice(Translator.translate("String_Node_Str"));
      }
    }
 else {
      LineTracer tracer=new LineTracer(player);
      Block b=tracer.getTargetBlock();
      if (b == null) {
        player.notice("String_Node_Str");
        return;
      }
      b.setY(b.getY() + 1);
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        Entity rider=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[2].toUpperCase()));
        mob.spawn(rider);
        player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1],args[2]));
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
  }
  if (args.length == 4) {
    if (!args[3].matches("String_Node_Str")) {
      player.notice(Translator.translate("String_Node_Str"));
      Canary.help().getHelp(player,"String_Node_Str");
      return;
    }
    int amount=Integer.parseInt(args[3]);
    LineTracer tracer=new LineTracer(player);
    Block b=tracer.getTargetBlock();
    if (b == null) {
      player.notice("String_Node_Str");
      return;
    }
    b.setY(b.getY() + 1);
    boolean spawnSuccess=true;
    for (int i=0; i < amount; ++i) {
      try {
        Entity mob=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[1].toUpperCase()),b.getLocation());
        Entity rider=Canary.factory().getEntityFactory().newEntity(EntityType.valueOf(args[2].toUpperCase()));
        spawnSuccess&=mob.spawn(rider);
      }
 catch (      IllegalArgumentException e) {
        player.notice("String_Node_Str");
      }
    }
    if (spawnSuccess) {
      player.message(Colors.YELLOW + Translator.translateAndFormat("String_Node_Str",args[1],args[2]));
    }
 else {
      player.notice(Translator.translate("String_Node_Str"));
    }
  }
}