bch2_btree_iter_peek_node() can return a NULL ptr (when the tree is
shorter than the search depth); handle this with an early return.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Fixes: https://lore.kernel.org/linux-bcachefs/5fc3c28b-c232-4ec7-b0ac-4ef220ddf976@moroto.mountain/T/Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>