Row access uses `row["sentry.dsc.root_project"]` without a presence/None check, then wraps it with `int(...)`. If Snuba returns rows where this column is missing (e.g., spans without a DSC root project tag) or where the value is None, this raises KeyError or TypeError, aborting the entire per-project volume computation for the organization. The sibling helper `_get_aggregate_int` was explicitly hardened in this same diff to handle None, but the group-by key was not, leaving an inconsistent safety posture.