Program: 81401
Project: 81401
Buggy source:
/** 
 * Spawn guard wolves to this prisoner to kill him
 * @param num Number of guards to spawn
 * @param location Spawning location
 * @param player Player, associated with this JailPrisoner
 */
public void spawnGuards(int num,Location location,Player player){
  List<BlockFace> checkedCorners=new ArrayList<BlockFace>();
  for (int i=0; i < num; i++) {
    Location spawn=null;
    for (int ci=0; ci < 4; ci++) {
      Block block=location.getBlock().getRelative(BlockFace.values()[ci]);
      if (!checkedCorners.contains(BlockFace.values()[ci]) && (block.getType() == Material.AIR || block.getType() == Material.STATIONARY_WATER || block.getType() == Material.WATER)) {
        spawn=block.getLocation();
        checkedCorners.add(BlockFace.values()[ci]);
        break;
      }
    }
    if (spawn == null) {
      checkedCorners.clear();
      for (int ci=0; ci < 3; ci++) {
        if (!checkedCorners.contains(BlockFace.values()[ci]) && location.getBlock().getRelative(BlockFace.values()[ci]).getType() == Material.AIR || location.getBlock().getRelative(BlockFace.values()[ci]).getType() == Material.STATIONARY_WATER) {
          spawn=location.getBlock().getRelative(BlockFace.NORTH).getLocation();
          checkedCorners.add(BlockFace.values()[ci]);
        }
      }
      if (spawn == null)       spawn=location;
    }
    Wolf guard=(Wolf)location.getWorld().spawnCreature(spawn,CreatureType.WOLF);
    if (!(guard.getWorld().getEntities().contains(guard))) {
      canSpawnGuards=false;
      return;
    }
    guard.setHealth(getJail().getSettings().getInt(Setting.GuardHealth));
    guard.setAngry(true);
    guard.setSitting(false);
    guard.setTarget(player);
    getGuards().add(guard);
    Jail.guards.put(guard,this);
  }
}

Fixed version (ground truth):
/** 
 * Spawn guard wolves to this prisoner to kill him
 * @param num Number of guards to spawn
 * @param location Spawning location
 * @param player Player, associated with this JailPrisoner
 */
public void spawnGuards(int num,Location location,Player player){
  List<BlockFace> checkedCorners=new ArrayList<BlockFace>();
  for (int i=0; i < num; i++) {
    Location spawn=null;
    for (int ci=0; ci < 4; ci++) {
      Block block=location.getBlock().getRelative(BlockFace.values()[ci]);
      if (!checkedCorners.contains(BlockFace.values()[ci]) && (block.getType() == Material.AIR || block.getType() == Material.STATIONARY_WATER || block.getType() == Material.WATER)) {
        spawn=block.getLocation();
        checkedCorners.add(BlockFace.values()[ci]);
        break;
      }
    }
    if (spawn == null) {
      checkedCorners.clear();
      for (int ci=0; ci < 3; ci++) {
        if (!checkedCorners.contains(BlockFace.values()[ci]) && location.getBlock().getRelative(BlockFace.values()[ci]).getType() == Material.AIR || location.getBlock().getRelative(BlockFace.values()[ci]).getType() == Material.STATIONARY_WATER) {
          spawn=location.getBlock().getRelative(BlockFace.NORTH).getLocation();
          checkedCorners.add(BlockFace.values()[ci]);
        }
      }
      if (spawn == null)       spawn=location;
    }
    Wolf guard=(Wolf)location.getWorld().spawnCreature(spawn,CreatureType.WOLF);
    if (!(guard.getWorld().getEntities().contains(guard))) {
      canSpawnGuards=false;
      return;
    }
    int health=getJail().getSettings().getInt(Setting.GuardHealth);
    if (health > guard.getMaxHealth()) {
      Jail.log.warning("String_Node_Str" + guard.getMaxHealth() + "String_Node_Str");
      health=guard.getMaxHealth();
    }
    guard.setHealth(health);
    guard.setAngry(true);
    guard.setSitting(false);
    guard.setTarget(player);
    getGuards().add(guard);
    Jail.guards.put(guard,this);
  }
}