fix case when parent_snapshot_id is 0

Author: chinmay-bhat

pyiceberg/table/snapshots.py

@@ -423,6 +423,6 @@ def ancestors_of(current_snapshot: Snapshot, table_metadata: TableMetadata) -> I
     """Get the ancestors of and including the given snapshot."""
     if current_snapshot:
         yield current_snapshot
-    if current_snapshot.parent_snapshot_id:
+    if current_snapshot.parent_snapshot_id is not None:
         if parent := table_metadata.snapshot_by_id(current_snapshot.parent_snapshot_id):
             yield from ancestors_of(parent, table_metadata)