[SOLVED] Cannot set block

I am making a plugin in which when you break a tree, if the block under it is dirt, it places a sappling. Now, this has not been working for me for anything, looked up tutorials and other help and cannot figure out what is wrong.

Code (Text):

 
//Checks for breaking a WOOD_BLOCK, LEAF_BLOCK
    @EventHandler
    public void onBlockBreak(BlockBreakEvent event){
        Player player = event.getPlayer();
        Block block = event.getBlock();
        World w = player.getWorld();
        Location location = block.getLocation();
        Location locUnder = event.getBlock().getLocation();
        locUnder.setY(block.getY() - 1);
        boolean c = check(block.getLocation(), w);
       
        int x = block.getX();
        int y = block.getY();
        int z = block.getZ();
       
        Block b = w.getBlockAt(x,y,z);
       
        if(block.getType() == Material.LOG && c == true){
            block.breakNaturally();
             
            if((locUnder.getBlock().getType() == Material.DIRT) || (locUnder.getBlock().getType() == Material.GRASS)){
            b.setType(Material.STONE);
            player.sendMessage("Block under is dirt!");
            }
 

Now I know that the IF is working because as you can see the player.sendMessage works ingame but the block does not change. Please help. Thanks

 

Omg thank you so much! How stupid am I? Thanks for pointing that out! It works fine now