Wait $level->dropItem($stump->add(0.4, 0.4, 0.4), Item::get($drop[0], $drop[1], $drop[2])); This is code bug line 157 in plugin ChopTree
You're trying to transform an object to an array. If what you're trying to drop the blocks items, getDrops() returns an array. https://github.com/pmmp/PocketMine-...04801782c/src/pocketmine/block/Block.php#L449
No you should drop the item of the block, so get the dropitem FROM THE BLOCK and drop it with the level