Fix: Require the cache for upstream deps in the scheduler (#5571)

Author: izeigerman

sqlmesh/core/scheduler.py

@@ -730,9 +730,8 @@ def _find_upstream_dependencies(
         parent_sid: SnapshotId,
         intervals_per_snapshot: t.Dict[str, Intervals],
         snapshots_to_create: t.Set[SnapshotId],
-        cache: t.Optional[t.Dict[SnapshotId, t.Set[SchedulingUnit]]] = None,
+        cache: t.Dict[SnapshotId, t.Set[SchedulingUnit]],
     ) -> t.Set[SchedulingUnit]:
-        cache = cache or {}
         if parent_sid not in self.snapshots:
             return set()
         if parent_sid in cache: