Merge pull request #21117 from owncloud/owner-file-exists

Only return an owner if the file exists + improved getUidAndFilename

diff --cc apps/files_sharing/lib/helper.php
Simple merge

diff --cc apps/files_trashbin/lib/trashbin.php
Simple merge

diff --cc apps/files_versions/lib/storage.php
Simple merge

diff --cc lib/private/files/view.php
Simple merge