Program: 57920
Project: 57920
Buggy source:
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void onBlockIgnite(BlockIgniteEvent event){
  Player player=event.getPlayer();
  Entity ignitingEntity=event.getIgnitingEntity();
  Block block=event.getBlock();
  BlockIgniteEvent.IgniteCause igniteCause=event.getCause();
  Location loc;
  if (block != null) {
    loc=BukkitUtil.getLocation(block.getLocation());
  }
 else   if (ignitingEntity != null) {
    loc=BukkitUtil.getLocation(ignitingEntity);
  }
 else   if (player != null) {
    loc=BukkitUtil.getLocation(player);
  }
 else {
    return;
  }
  PlotArea area=loc.getPlotArea();
  if (area == null) {
    return;
  }
  if (igniteCause == BlockIgniteEvent.IgniteCause.LIGHTNING) {
    event.setCancelled(true);
    return;
  }
  Plot plot=area.getOwnedPlotAbs(loc);
  if (player != null) {
    PlotPlayer pp=BukkitUtil.getPlayer(player);
    if (plot == null) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_ROAD)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_ROAD);
        event.setCancelled(true);
      }
    }
 else     if (!plot.hasOwner()) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_UNOWNED)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_UNOWNED);
        event.setCancelled(true);
      }
    }
 else     if (!plot.isAdded(pp.getUUID())) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
      }
    }
 else     if (!plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
      event.setCancelled(true);
    }
  }
 else   if (ignitingEntity != null) {
    if (plot == null || !plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
      event.setCancelled(true);
      return;
    }
    if (igniteCause == BlockIgniteEvent.IgniteCause.FIREBALL) {
      if (ignitingEntity instanceof Fireball) {
        Projectile fireball=(Projectile)ignitingEntity;
        Location location=null;
        if (fireball.getShooter() instanceof Entity) {
          Entity shooter=(Entity)fireball.getShooter();
          location=BukkitUtil.getLocation(shooter.getLocation());
        }
 else         if (fireball.getShooter() instanceof BlockProjectileSource) {
          Block shooter=((BlockProjectileSource)fireball.getShooter()).getBlock();
          location=BukkitUtil.getLocation(shooter.getLocation());
        }
        if (location != null && (location.getPlot() == null || !location.getPlot().equals(plot))) {
          event.setCancelled(true);
        }
      }
    }
  }
 else   if (event.getIgnitingBlock() != null) {
    Block ignitingBlock=event.getIgnitingBlock();
    if (igniteCause == BlockIgniteEvent.IgniteCause.FLINT_AND_STEEL) {
      if (plot == null || !plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
        event.setCancelled(true);
        return;
      }
      if (BukkitUtil.getLocation(ignitingBlock.getLocation()).getPlot() == null) {
        event.setCancelled(true);
        return;
      }
      if (!BukkitUtil.getLocation(ignitingBlock.getLocation()).getPlot().equals(plot)) {
        event.setCancelled(true);
        return;
      }
    }
    if (igniteCause == BlockIgniteEvent.IgniteCause.SPREAD || igniteCause == BlockIgniteEvent.IgniteCause.LAVA) {
      if (plot == null || !plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
        event.setCancelled(true);
        return;
      }
      if (BukkitUtil.getLocation(ignitingBlock.getLocation()).getPlot() == null) {
        event.setCancelled(true);
        return;
      }
      if (!BukkitUtil.getLocation(ignitingBlock.getLocation()).getPlot().equals(plot)) {
        event.setCancelled(true);
        return;
      }
    }
  }
}

Fixed version (ground truth):
@EventHandler(priority=EventPriority.HIGHEST,ignoreCancelled=true) public void onBlockIgnite(BlockIgniteEvent event){
  Player player=event.getPlayer();
  Entity ignitingEntity=event.getIgnitingEntity();
  Block block=event.getBlock();
  BlockIgniteEvent.IgniteCause igniteCause=event.getCause();
  Location loc;
  if (block != null) {
    loc=BukkitUtil.getLocation(block.getLocation());
  }
 else   if (ignitingEntity != null) {
    loc=BukkitUtil.getLocation(ignitingEntity);
  }
 else   if (player != null) {
    loc=BukkitUtil.getLocation(player);
  }
 else {
    return;
  }
  PlotArea area=loc.getPlotArea();
  if (area == null) {
    return;
  }
  if (igniteCause == BlockIgniteEvent.IgniteCause.LIGHTNING) {
    event.setCancelled(true);
    return;
  }
  Plot plot=area.getOwnedPlotAbs(loc);
  if (player != null) {
    PlotPlayer pp=BukkitUtil.getPlayer(player);
    if (plot == null) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_ROAD)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_ROAD);
        event.setCancelled(true);
      }
    }
 else     if (!plot.hasOwner()) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_UNOWNED)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_UNOWNED);
        event.setCancelled(true);
      }
    }
 else     if (!plot.isAdded(pp.getUUID())) {
      if (!Permissions.hasPermission(pp,C.PERMISSION_ADMIN_BUILD_OTHER)) {
        MainUtil.sendMessage(pp,C.NO_PERMISSION_EVENT,C.PERMISSION_ADMIN_BUILD_OTHER);
        event.setCancelled(true);
      }
    }
 else     if (!plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
      event.setCancelled(true);
    }
  }
 else {
    if (plot == null) {
      event.setCancelled(true);
      return;
    }
    if (ignitingEntity != null) {
      if (!plot.getFlag(Flags.BLOCK_IGNITION).or(false)) {
        event.setCancelled(true);
        return;
      }
      if (igniteCause == BlockIgniteEvent.IgniteCause.FIREBALL) {
        if (ignitingEntity instanceof Fireball) {
          Projectile fireball=(Projectile)ignitingEntity;
          Location location=null;
          if (fireball.getShooter() instanceof Entity) {
            Entity shooter=(Entity)fireball.getShooter();
            location=BukkitUtil.getLocation(shooter.getLocation());
          }
 else           if (fireball.getShooter() instanceof BlockProjectileSource) {
            Block shooter=((BlockProjectileSource)fireball.getShooter()).getBlock();
            location=BukkitUtil.getLocation(shooter.getLocation());
          }
          if (location != null && !plot.equals(location.getPlot())) {
            event.setCancelled(true);
          }
        }
      }
    }
 else     if (event.getIgnitingBlock() != null) {
      Block ignitingBlock=event.getIgnitingBlock();
      Plot plotIgnited=BukkitUtil.getLocation(ignitingBlock.getLocation()).getPlot();
      if (igniteCause == BlockIgniteEvent.IgniteCause.FLINT_AND_STEEL && (!plot.getFlag(Flags.BLOCK_IGNITION).or(false) || plotIgnited == null || !plotIgnited.equals(plot)) || (igniteCause == BlockIgniteEvent.IgniteCause.SPREAD || igniteCause == BlockIgniteEvent.IgniteCause.LAVA) && (!plot.getFlag(Flags.BLOCK_IGNITION).or(false) || plotIgnited == null || !plotIgnited.equals(plot))) {
        event.setCancelled(true);
      }
    }
  }
}