Add proper handling of files without permissions

Now a file gets its directory permissions only if it contained no
permissions (they were undefined or null), but not if its permissions
were set to "NONE".

Besides that, now file actions that do not require any permission on the
file to be performed can be used on files that have no permissions.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>