Fix memory leak of world data when quitting a world.
This is a workaround to an FML bug: in SSP onConnectionClosed doesn't get always called for server side, this way the PacketHandler can't remove the PlayerInfo instance for the server and this holds references to world data.
Fix StackOverflow when chopping big trees.
No need to make a recursion vertically since we are already moving by "layers" with the while loop.