bcachefs: Make snapshot_is_ancestor() safe

Snapshot table accesses generally need to be checking for invalid
snapshot ID now, fix one that was missed.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-04-04 15:50:26 -04:00
commit 01e5f4fc0f