Allow re-using already known fileinfo when calculating folder sizes
Remove assert since the root size of the home storage is no longer calculated
Check if fields we need are actually set to prevent errors
Merge branch 'master' into foldersize-reuse

Conflicts:
lib/private/files/cache/homecache.php
Merge pull request #7477 from owncloud/foldersize-reuse

Allow re-using already known fileinfo when calculating folder sizes