Fix handling of deleted pages in getAffectedUsagesByPage
getAffectedUsagesByPage should skip unknown pages, instead of
diying with a StorageException.
Bug: T87009
Change-Id: I27d79989daf0c82d3fdef9b21a29fc081cd28b4b
(cherry picked from commit 57e85d2fc678c8edfbeb25979738d085cbd8c12c)